& wireless world...tf 2604 voltmeter £425 tf 2702 inductor analyser £950 tf 2905/8 tv pulse...

TH=01111:42G11101:11112011* INAL

ELECTRONICS& WIRELESS WORLD

JULY 1987

Capacitors -techniquesandapplications

Curls, grads,divs and dels

Real-timecolour palette

Mobile radioupdate

V.h.f. voltage -

controlledoscillator

Class Bcrossoverdistortion

Denmark DKr. 63.00 Germany DM 12.00 Greece Dra. 680.00 Holland DFI. 12.50 Italy L 6500 Spain Ptas. 700.000

Singapore SS 11.25 Switzerland SFr. 9.50 USA S 6.50.

CliECTRONIC BROKERSThis is just a sample of our huge inventory - contact us with your requirements.OSCILLOSCOPES

Hewlett Packard180 TR 100MHz Scope Mainframe

(Mint)PhilipsPM3266 100MHz Storage ScopePM3305P 35MHz Digital Storage.] onlyPM3540 Logic Anal/ScopeTektronix465B/DM44100MHz Scope/DMM4658100MHz Scope475A/DM44 200MHz Scope/DMM485350MHz Scope608 Monitor634 opt 1,20 Display

Monitor5223 Scope M/F (Mint)71041 GHz Scope M/F7603100MHz NVF7704A 200MHzMainframe £28507834 Fast Storage ScopeM/F £7500R7603 100 MHz RackMINT M/F £17507904 500 MHz ScopeM/F £5500A large selection of7000 series plug -insavailable at up to 60%saving on list. Pleasecall for quotations.

ANALYSERS

£950

£3950£1925£950

£1595£1450£2500

£3950£1250

£395£3600

£16000£1500

Hewlett Packard141T DisplayMainframe £20003580A SpectrumAnalyser3582A SpectrumAnalyser4193A ImpedanceAnalyser8552B IF Section

£3000

£7500

£5250£1850

8553B RF Section,110MHz £2650MarconiIF 2300A Mod Meter £495TF 2370 110MHz SpectrumAnalyser £7250TF 2371 200MHz Spectrum Analyser £6500Tektronix7L14 Spectrum Analyser P. In308 Data Anal ser

£9250£600

SIGNAL SOURCESHewlett Packard4204A Digital Oscillator8007B Pulse Generator8011A-001 Pulse Generator

20MHz8601 A SweepGenerator86408/001/002 Signal Generator

1024MHz86260A Sweep Gen. Plug-in12.4 -18GHzMarconi2015-1 ANVFM Signal

GeneratorTF 2002B AM/FM Signal Generator

£200£750

£400£1000

£4250

£1500

£675£500

PhilipsPM5519ITV Pattern GeneratorWavetek1 84MHz Sweep Generator1080 1GHz Sweeper

£595

£425£1500

HEWLETT PACKARDCOMPUTERS

RTE85A Microcomputer86A Microcomputer110 (45710BU) The Portable'150B Touchscreen2673A Thermal Printer6940B Multiprogrammer7470A opt 001/002 A4 2 -pen plotter7475A opt 002 A3/A46 -pen plotter7910H opt 015 Disk Drive82913A 12 inch Monitor82938A HPIL Interface82939A Serial Interface82940A GPIO Interface9111A Graphics Tablet9121D Single -sided Disc Drive91 22D Dual Double -sided Disc Drive91 33XV 1 5MB & 270KB Disk Drive

£995£600£950£350£425£950£575

£1050£200

£75£150£100£250£825£450£775£600

9845A Desk Top Computer9816A Personal Computer9825A opt 001-002 Desk Top

Computer98256A 256K RAM board,

series 200991 5AComputer

£1650£2400

£700

£250£600

GENERAL PURPOSE T &FarnellSSG 520 TTS 520 Transmission

Test Set

Fluke7220A Comms. Freq. Counter £350

Hewlett Packard4282A-001 Digital High

Capacitance Meter £750436A Power Meter £1050

467AAmplifier £6003403C True RMS

Voltmeter £18503406A Sampling

0 Voltmeter £12503465A 4' DigitD.M.M. £1005300B + 5305B 1300MHz Counter £4955381A 80 MHzCounter £2258447A Amplifier £4008447D Amplifier £600MarconiTF1 245A Q meter

£750TF 1246Oscillator £500TF 1313A LCR Bridge0.1% £750

TF 2173Synchroniser

for2016 £450TF 2603 RF

Millivoltmeter £300TF 2604 Voltmeter £425

TF 2702 InductorAnalyser £950

TF 2905/8 TV PulseGenerator £650

TF 2915 Data Monitor £1200TF 2950/5 Mobile Radio T.S. £1350PhilipsPM5580 IF Modulator £3000PM5581 RF Convertor £1000PM5582 RF Convertor £1000Tektronix520AVectorscope(NTSC)521A PAL VectorscopeSi Sampling HeadS.3A Sampling Head1411C opt 03 TV Signal GeneratorA6901 Isolation Monitor4041 System ControllerP6451 DA ProbePM 102 Personality ModulePM 108 Personality Module

£4275

£3750£3950£850

£1250£5500

£275£4650

£250£500£650

SEND NOW FOR OURLATEST BROCHURE

All prices are exclusive of VAT and correct at time of going to press Carriage and packing charges extra A copy of our trading conditions is available on request

o(

Electronic Brokers

)

) Electronic Brokerso 140-146 Camden Street, London NW1 9PBo U Fax: 01-2677363. Telex: 298694. Tel: 01-2677070ENTER I ON REPLY CARD

CONTENTSJULY 1987

iallatamsCOVER

Research into biohybrid integrated circuitsinvolves interconnections betweenneurons. Nerve cells in this electron

micrograph are between a quarter and atenth of a micron across. Last month's

cover, which carried an incorrect caption,was an internal view of Motorola's 68020

32bit microprocessor.

NEW -WAVE ARCHITECTURE

671The new architecture makes all bus devicesintelligent so that bus activity is local to the

processors, thus leaving the bus free fordata transfer

by David Hunt and Keith Hodson.

MOBILE RADIO UPDATE678

This years MRUA conference coincided withpublication of the government -sponsored

report on spectrum deregulation.

EUROPE'S CAPACITORMARKET

688Historically, the somewhat slow -moving

and technologically mature capacitorindustry has been overlooked by investment

interest and p.r. hype. But there arechanges afoot, both in market and industry...

by Keith Thomas

CAPACITOR TECHNOLOGIESCOMPARED

690Engineers should have a good appreciation

of the cost of various technologies for agiven capacitance value

by Martin Baker

TERMINATIONS FORCERAMIC CHIP CAPACITORS

692The low cost of nickel barriers vs the

reliability of silver -palladium.

MAXWELL'S E.M. THEORYREVISITED

697."If Maxwell's theory is about to be displaced

we might take a nostalgic look at it onceagain"

by Joules Watt

VOLUME 93 NUMBER 1617

By 1990 a typical car might contain 500capacitors, say AVX of Aldershot. leadingto a very large volume of production if theestimate of 10 million new cars in Europeis realistic. See page 688 for an analysisof Europe's capacitor market.

PRESCALERS EXCEED 3GHZ

699Bipolar i.c. technology has produced fastprescalers with a phase noise and speed -

power performance better than with GaAs.

INTERMURAL TV SIGNALS

705A well -placed dipole can often give betterresults than indoor Yagi or logarithmic

arrays.

UNIVERSAL VCOWITH LOW PHASE NOISE

707Analysis of noise behaviour for a variety of

v.h.f. transistors shows that a j-fetproduces the lowest phase noise

by A. Decker

MODELLING YAGI-UDAANTENNAS

710Suite of Pascal programs calculates gain,

impedance, current distribution andradiation pattern for any geometry, element

thickness and operating frequency.by C.J. Railton

PIONEERS: Bell

716by W.A. Atherton

68000 -FAMILY PASCAL MACHINE

718If you are about to decide on a computerlanguage for your next industry controlsystem, one of the new breed of Pascal

compilers may be ideal.by William Stanley

VIDEO FRAME STORE721

Fast look -up table enables frame store tomanipulate moving images in real time for

flicker -free effectsby D.E.A. Clarke

CACHE MEMORY DESIGN

727External cache with 25ns rams can takecare of repetitive loops with the 68020

by D.Burns and D.Jones

EPROM PROGRAMMER -2

735by B.J. Sokol

CROSSOVER DISTORTION INCLASS B AMPLIFIERS

739Detailed tests on three amplifier modes,

including a non -switching form of class B,give rise to some interesting conclusions

by Erik Margan

LEETRONEX 87761

Under Leeds University's Department ofElectrical and Electronic Engineering this

exhibition claims to be the bestin electronics outside London.

COMMENT 667

FEEDBACK 683

CIRCUIT IDEAS 695, 706

APPLICATION NOTES 701

TELECOM TOPICS 731

RESEARCH NOTES 733

SATELLITE SYSTEMS 737

PRODUCTS 743 to 751

RADIO BROADCAST 753

RADIO COMMS 755

TV BROADCAST 757

UPDATE 762

APPOINTMENTS 764

ADVERTISERS INDEX 768ELECTRONICS & WIRELESS WORLD 665

...011.1111

whietriammriUSED TEST & COMPUTER EQUIPMENT

FULL PERFORMANCE TO ORIGINAL SPECIFICATION==* ALL ITEMS ARE COVERED BY OUR COMPREHENSIVE PARTS & LABOUR GUARANTEE ***

LOGIC ANALYSERS &DIGITAL TESTEQUIPMENT

HEWLETT PACKARD1630G Logic state &timing.65ch. 100MHzclock...£7950

4951A/1/100 PortableProtocol Analyser forserial data..£2500

TEKTRONIX834 Datacom/ProtocolAnalyser...£2000

OSCILLOSCOPES

PHILIPSPM3266 100MHz Faststorage.Dual trace dualtimebase...£2950

TEKTRONIX2215 60MHz dual tracewith delay...£625

2445 150MHz fourtrace.Dual timebase.£2190

2465 300MHz four tracewith delay..£3200

7623A/7A18/7B53A 75MHzFast storage.Dual trace.Dual t/base..£1500

SPECTRUM ANALYSERS

HEWLETT PACKARD141T/8552B/8555A System0.01-18GHz.£7500 or with model8445 pre-selector..£9000

3561A/001 DynamicSignal Analyser....£7950

MARCONIff7YNT 110MHz analyserwith trackinggenerator....£6850

SOLARTRON1200 Dual channel L.F.SignalProcessor/Analyser.£7250

SIGNAL SOURCES

MARCONI2019 1GHz AM/FM phaselocked.HP-IB..£2950

PHILIPSPM5190 1mHz-2Mhz phaselocked.HP-IB£1050

SPECIAL OFFERS

HEWLETT PACKARD1630D LOGIC ANALYSER

State/Timing/Glitch43ch. 100MHz.Clock mux..£4250

WATANABEMC6601-6Z

CHART RECORDER

6ch.flatbed. Overlappingpens. I/P voltages lmV-500V..£500.

ATLANTIC RESEARCHInterview 4600

PROTOCOL ANALYSER

Int. memory + datatape. Up to 19.2kbps..£3250

MICRO DEVELOPMENTSYSTEMS

INTELSeries 2Series 3Series 4 & PDS seriessystems are allavailable.CHECK NOW FOR BESTPRICES:

HEWLETT PACKARD64100A/041 Logicdevelopment station.....£5900

64600 Logic TimingAnalyser...£2500

A WIDE RANGE OF THISSERIES EQUIPMENT ISAVAILABLE. CALL US FORTHE LATEST INFORMATION!

COMPUTERS ANDPERIPHERALS

CENTRONICS353 200cps dot matrixprinter. Centr. & RS232I/F. +NLQ mode ..£350

EPSONFX100 MatrixPrinter...£.325

MX100 MatrixPrinter...£.195

HEWLETT PACKARD7475A/2 Eight penplotter HP-IB..£800

82901A Dual Disc DriveHP-IB...£150

9817 Modular computerworkstation....£1800

9826A Technical computer/ controller. Internaldisc...£1500

FULL SPECIFICATIONS OFTHESE ITEMS AREAVAILABLE ON REQUEST !

Prices EXCLUDE delivery& V.A.T.

THE ABOVE EQUIPMENT IS JUST A SMALL SELECTION FROM OUR CURRENT STOCK !

Stocks are always changing: If your requirement is not listed thenplease phone: WE MAY WELL BE ABLE TO HELP YOU !

%Er 01-943 4477WE ALSO BUY TOPUALITYUNDER UTILISED EQUIPMENT

Cardwell Carstolf:CARSTON ELECTRONICS LTD. 3 Park Rd. Teddington. Middx. TW11 OAF Tel. 01-943-4477 Telex. 938120 CARLEC-G

ENTElt 19 ON REPLY CARD

COMMENT

EDITORPhilip Darrington

DEPUTY EDITORGeoffrey Shorter, B.Sc.

01-661 8639

TECI INICAI, EDITORMartin Eccles01-661 8638

PROJECTS EDITORRichard Lambley

01-661 3039

NEWS EDITORDavid Scobie01-661 8632

DESIGN & ILLUSTRATIONAlan Kerr

01-661 8676Roger Goodman

ADVERTISEMENT MANAGERMartin Perry01.6613130

Michael Downing01-661 8640

CLASSIFIED EXECUTIVESusan Platts01-661 3033

ADVERTISING PRODUCTIONBrian Bannister

(Make-up and copy)01-661 8648Jackie Perry01-661 8649PUBLISHER

Shobhan Gajjar01-661 8452

Embarrasde richesse

Whenever an engineering development to improve services is madepossible, the broadcasting organizations are at pains to ensure thatexisting equipment is not rendered obsolete or, if it is made

incompatible, long periods are allowed for any necessary changeover. One cancite the move to 625 -line television: the introduction of f.m. radio; the start ofcolour: the incorporation of teletext - all these were brought about painlessly,at no cost to those users who did not want the new service, except for the625 -line change which took place over more than 20 years, and in some caseswithout the user even being aware of the development. These organizationshave a duty to bring about change in this way and take a great deal of trouble todo so. They are concerned chiefly with providing the best possible service andthe profit motive is absent.

But what of development in the rest of the consumer electronics market? Itappears that no such scruples can exist alongside the need to create newmarkets. Each new development that emerges from the multinationals is, ofcourse, an improvement on previous products, but at what cost to the public?

Admittedly, there are those who will acquire the newest, simply because it isavailable. But, if the majority have been persuaded to buy cassette recordersand black disc turntables at great expense, it is surely not unnatural for themto feel aggrieved when the next development uses optical discs and is totallyincompatible with their equipment. If a music lover possesses a collection ofcassettes, built up over ten years, does not the impending introduction ofdigital audio tape fill him with alarm and despondency?

It would be naive to expect the manufacturers of domestic electronicequipment collectively to refrain from introducing new techniques to themarket until the previous generation of equipment had had a reasonable run,but there must surely be a less cynical way of progressing than to rendercollections of hardware and "firmware" obsolete at a stroke. The very least thatcan be done is to allow existing technology an extended period of obsolescence.

The consumer society is becoming, or has become, the victim of the pursuitof technology for its own sake. So far, society has been tolerant and even eagerfor new technology, but in the face of time scales of introduction andobsolescence which are shrinking to the point of bewilderment, it musteventually begin to react: the diminishing returns of "investment" in newmethods of playing recorded music or watching television cannot escape noticefor ever.

El. Mon 'us & World is published monthlyUSPS 6875414 Curnmt issue price (1.95, back issues naavailable'(2.10 at Itetad and Trade Counter. Units l& BanksideIndustrial Centre. Iloptim Street. London SE1 Telephone:01412/4 :1567. By post, current issue £2.25. back issues 'ifAValtabil-1 £2.50. Order and payments to 301 EIrrimmt,and Wireless World. Quadrant Douse. The Quadrant.Stilton. Surrey SM2 5AS. Cheques should be payable toReed Business Publishing Ltd. Editorial & Advertisingoffices: EWW Quadrant House. The Quadrant. Sutton.Surrey SM2 5AS. Telephones: Editorial 01-661 3614.Advertising 01.661 3130 111-661 8469 Telex: 892010B1SPRS B IEE1'. Facsimile: 014;61 3948 'Groups II &Beeline: 01.661 M978 or 01-661 8486.:1111 baud. 7 data bits,even parity. stop -bit. Send ctrl -Q. then EWW to start:NNNN tii sign MT. Subscription rates: I year 'normal

ratio 123.40 (IN and £28.50 outside (IE. Distribution:quadrant !louse. The Quadrant. Sutton. Surrey SM2 5ASTelephone 01-661 32414. Subscriptions: ()Afield !louse.l'errymount Road. Hayward': Heath. Sussex 81116 :11)11.Telephone 04444 59188. Please notify a change of addressUSA: $116.00 airmail. Reed BusinessPublishing USA'. Subscript imis Office. 205 E. 42nd Street.NY 10117. Overseas advertising agents: France andBelgium: Pierre Mussard, 18-20 Place de la Madeleine.Paris 750194. United Stales of America: Lay Feitintaii.Reed Business Publishing lad. 2115 East 42nd Street.New York. NY 10017 Telephone 12121 887.2080 Telex23827. USA mailing agents: Mercury Airfreight Inter-national Ltd. Inc.. 10161 Englehard Ave, Avenel N.J. 071811.2nd class postage paid :it Rahway N.J. Postmaster - sendaddress to the almve.

)keel Business Publishing lad 1987. ISBN 19143 61162

ELECTRONICS & WIRELESS WORLD 667

GASFET RF PREAMPLIFIERSThese amplifiers provide the best noise performance available. Suitable for laboratory work or masthead use.Aligned to your specified frequency in the range of 30-1000MHz.

TYPE 9006 N.F. 0.6 dB. Gain 10-40 dB variable. In the range 30-250 MHz . . . £71 £3 p&p. TYPE 9006FM As9006. Band II 88-108 MHz . . . £71 + £3 p&p. TYPE 9002 Two stage Gasfet preamplifier N.F. 0.7 dB. Gain 25 dBadjustable. High Q filter. Tuned to your specified channels in bands IV or V . . . £93 + £3 p&p. TYPE 9004UHF two stage Gasfet preamplifier N.F. 0.7 dB. Gain 25 dB adjustable. High Q filter. Aligned to your specifiedfrequency in the range 250-950 MHz . . £93 + £3 p&p. TYPE 9035 Mains power supply unit for abovepreamplifiers . . . £27.00 + £4 p&p. TYPE 9010 Masthead weatherproof unit for above preamplifiers . . . £11 +£3 p&p.

RF SIGNALS SOURCES 10 MHz -1 GHzHigh stability phase locked oscillators operating directly on the signal frequency using a low frequencyreference crystal. Miniature modules capable of accepting NBFM or FSK up to 3 KHz deviation which willeffectively replace expensive signal generators in the lab to provide single specified frequencies. Linearamplifers are available to increase output power. TYPE 8034 Specify output in the range 10-150 MHz. Output10 mW ( + 10 dBm) . . . £109 + £3 p&p. TYPE 8036 Specify output in the range 150-1000 MHz. Output 10mW . . .

£163 + £4 p&p.FREQUENCY CONVERTERS

Transmitting frequency converter provides the performance required for television retransmission systems.TYPE 9113 . . . £324 + £6 p&p. Receiving frequency converter for weak signal reception . . . TYPE 9114. . . £324 + £6 p&p.

BAND II FM TRANSMITTERSingle channel high stability phase locked loop FM exciter. 50 watts RF output. Complete in 19" racking casewith mains power supply and fan cooling.

TYPE 9292A (Mono) . . . £1496 + £40 p&p TYPE 9292B (Stereo) . . . £1794 + £40 p&pComplete amplifier and retransmission systems supplied with connectors. Comprehensive range of RF linearpower amplifiers also available. Write or phone for full technical information.

Please add 15% VAT on total for UK sales. Please contact sales office for overseas post and packing rates.

RESEARCH COMMUNICATIONS LTDUNIT 3, DANE JOHN WORKS, GORDON ROAD,

CANTERBURY, KENT CT1 3PPTELEPHONE CANTERBURY (0227) 456489

DESIGN, DEVELOPMENT ANDMANUFACTURE OF RF

COMMUNICATIONS EQUIPMENT

ENTER IS ON IMPLY '.14

PINEAPPLE SOFTWAREPrograms for BBC computers with disc drive. FREE updating service on all software.

DIAGRAMStill the only drawing program avai able for the BBC micro which gives you the ability to draw really large

diagrams and scroll them smoothly around the screen stopping to edit them at any time if requiredPineapple s unique method of storing the diagram information on disc means that the size of diagrams is

limited only by the free space on disc and not the amount of computer memory you have available IA blank80 track disc will allow up to 39 mode 0 screens of diagram(

The superb print routine( supplied with the program enable large areas of the diagram to be printed in asingle print run in a number of different sizes and rotated through 90 deg if required Full use can also bemade of printers which have a wider than normal carriage available

The program is fully compatible with the Marconi Tracker ball described below

PLEASE STATE 40 or 80 TRACK DISC& WHETHER STANDARD BBC or MASTER VERSION IS REQUIRED

PRICE £25.00 VAT

DIAGRAM UTILITIESA suite of six utility programs w' ''' f) .ftram drawing program The utilities

include the saving and loading of areas of diagram to and from disc Tne ability to disblay the whole of yourlarge diagram on the screen at one time tin either 4*4 or 8*8 screen format) Tne addition of borders andscreen indents to diagrams. and the ahrav I,. shift a whole diagram in any direction

PRICE £10.00 + VAT

PCBThis new releaSe from Pineapple is a printed circuit board draughting aid which is aimed at producing

complex double sided PCBs very rapidly using a standard BBC micro and any FX compatible dot-matrixprinter

The program is supplied >n EPROM and will run with any 32k BBC micro (including Master series) Alsosupplied is a disc containing a sample PCB layout to demonstrate the programs features

By using an EPROM for the program code the maximum amount of RAM is available for storing componentlocation and ASCII identification files etc I Up to 500 components and 500 ASCII component descriptionsmay be stored for a given layout) These is no limit to the number of tracks for a given PCB, aitnougn themaximum size of board is restricted to 8- ' 5 6 -

Using a mode 1 screen. tracks on the top side of the board are shown in red. while those on the undersideare blue Each side of the board may be shown individually or superimposed A component placement screenallows component outlines lo be drawn for silk screen purposes and component numbers entered on thisscreen may be displayed during track routing to aid identification of roundels

The print routines allow separate printouts of each side of the PCB in a very accurate expanded definition1 1 or 2 1 scale enabling direct contact printing to be used on resist covered copper clad board

This program has too marry superb features to describe adequately here. so please write or phone for moreinformation and sample prinouts

PRICE £85.00 VAT

MARCONI TRACKER BALLThis high quality device comes with it s own Icon Artmaster drawing program and utilities tuenable it to be

used in place of keyboard keys Joysticks or with your own programsFor Model B & B with icon Artmaster) 460 00 VAT Bare Trackman Ino software) 449 00 VATFor Master Series with Pointer ROM1 460 00 VAT Pointer ROM available separately 412 50 VAT

P&P on Trackerballs V 75

TRACKERBALL ADAPTORSConverter leads to enable the TraCkerball to run mouse software and the mouse to run trackerball software

Iinc DIAGRAM) Please state which way round when ordering

PRICE £8.00 t VAT

ADFS Utilities ROMADU is a new product which will prove invaluable to all users of the ADFS (Including Winchester ownersl

The ADU Rom allows direct access to utilities which previously required the use of the ADFS utilities disc

Many novel features are included in the commands allowing such facilities as the copying plan the Meson a DESdisc onto ADFS in a single pass and Backing up between discs of different size (including Winchesters)

There is also a very powerful sector editor with automatic correction of CRC bytes and a menu routine with over30 possible operations on ADFS discs

Please write or phone for more details

PRICE £29.00 VAT

MITEYSPICEA new addition to our range 01 engineering software Miteyspice is a very powerful DC and AC analogue circuit

simulator package with graphic display for any model BBC computer

As well as ail the usual facilities available with this type of program non-linear effects. small signal noisemeasurements and sweeps may be performed Component values may be swept. allowing component tolerances tobe investigated as well as thermal performance etc Comprehensive transistor modelling is incorporated using a 20parameter Ebers Moll description The program is supplied on disc with a very comprehensive 49 page manualPlease write or phone for more i,!.,nt

PRICE £119 VAT P&P FREE

ALL CI RIDERS scnur By RETURN OF POST

luz. 39 Brownlea Gardens, Seven Kings, Ilford, Essex 1G3 9NL. TA` Tel: 01-599 14760ENTER 47 ON REPLY CARD

668 ELECTRONICS & WIRELESS WORLD

ADCOLA

4

SOLDERINGSTATION 1456

macor.

THE ALL BRITISHSOLDERING EQUIPMENTMANUFACTURERS

A

COSTS LessTHAN L60

plus p & p and VAT

adjustable temperature simple plug in 4.75mm tipsin handle full supporting tip range

electronic thermostat control low voltage power pack- no moving parts 24v 50v AC

spike and potential free

DCOLP\rit.ve ,esWeir

ELECTRONIC PRODUCTION EQUIPMENT

FOR FULL DETAILSon all ADCOLA equipmentcontact Sales Department...

ADCOLA PRODUCTS LIMITED Gauden Road London SW4 6LHTelephone Sales (01) 622 0291 Telex 21851 Adcola GSales Offices also at Bristol Bournemouth Preston Glasgow

ENTER :16 ON It CARD

DM 105 - Pocket DVM fromA meter to literally suit allpockets - including the onethat holds the wallet!Its small size offers easy one hand operation, with large, clear,wide-angle display.But small does not mean delicate; the DM105 can withstand a 12inch drop without damage, due to its glass epoxy PC boards.shock mounted display and through thermoplastic case.Overloads are handled with similar certainty; the resistancerange is protected up to 500 dc. AC voltage range to 14XIV rmsand DC voltage ranges up to 1000V.Battery life is typically 2000 hours and a LO BATT indicatorsignals 20% battery life remaining.RangesDC Volts: 2V, 20V, 200V, I kVAC Volts 200V, 750VFreq Range: 45Hz - 450HzDC Current: 2 mA. 20 mA,

2(X) mA, 2AResistance: 2K. 20K, 200K, 2MDC Accuracy:

-± (0.5% reading - 2 digits)Size: 130 x 75 x 28mmWeight: I95gAccessories: Battery, test leadsand manual.

Price £24.75 Inc VATPlease add 70p for post and packing.

This is just one of our range of quality Analogue and Digitalmultimeters.

Full details and specifications from:

Cirkit Distribution LtdPark Lane, Broxbourne, Herts ENIO 7NciTelephone ( 0992) 444111 Telex: 22478

TR \ I W. ENQUIRIES WELCOME:

Access

VISA

ELECTRONICENGINEERS

serious CAD atlighthearted prices

ThoseEngineers

- reallyusefulpeople

IBM UsersFor PC

softwareplease seeour advert

on page 669

Probe wound Miteyspice'scomputer model of your circuit.More informative, more fun andfaster than a breadboard. Plot theAC & DC characteristics. quantitybandwidth with the digitisingcursor, sweep compone-its,investigate temperature and noise(20 param Ebers Moll model) andwhen perfect, lay it out and etch itaccurately with PCB using anordinary DM printer. Theseprograms have too many superbfeatures to cover here, please sendfor details.

* Just released *MITEYSPICE

incorporating the unbeatableMicrospice circuit simulator

(£119 r VAT)

P.C.B.Pineapple's acclaimed "a utility Ithoroughly recommend" JulianRogers Micro User March '87circuit board drafting program

(£85 + VAT)

Postal address, callers by appointmentTel: 106a Fortune Green Road Tlx:

01-435 West Hampstead 89505112771 London NW61 DS Mari, km mailbox

23332001

THOSE ENGINEERS Ltd(also at Fairoaks Airport, Chobham)

ENTER 55 ON REPLY CARD

ELECTRONICS & WIRELESS WORLD

ENTER:is oN REPLY CARD

669

The Archcr Z80 6I)CThe SDS ARCHER - The Z80 based single boardcomputer chosen by professionals and OEM users.* Top quality board with 4 parallel and 2 serial ports,

counter -timers, power -fail interrupt, watchdog timer,EPROM & battery backed RAM.

* OPTIONS: on board power supply, smart case,ROMable BASIC, Debug Monitor, wide range of I/O &memory extension cards.

from £185 + VAT.ENTER 45 ON REPLY CARD

The nowman 68000 613CThe SDS BOWMAN - The 68000 based single boardcomputer for advanced high speed applications.* Extended double Eurocard with 2 parallel & 2 serial

ports, battery backed CMOS RAM. EPROM, 2 counter -

timers, watchdog timer, powerfail interrupt, & anoptional zero wait state half megabyte D -RAM.

* Extended width versions with on board power supplyand case.

from £295 + VAT.ENTER 46 ON REPLY CARD

6hcrwood L)alacSystems LtdSherwood House, The Avenue, Farnham Common, Slough S1,2 3JX. Tel. 02814-5067

Ath4agt-

TRAINING FOR TRAINERSLAB -VOLT will be conducting a series of one day seminars on thefollowing technologies:

ROBOTICS - CONTROL DIGITAL - MICROPROCESSORS ELECTRICITY - ELECTRONICS CIRCUIT CONSTRUCTION TELECOMMUNICATIONS

Audio visual presentations and hands-on experience will be the main part ofthe seminars.A certificate of achievement can be obtained upon satisfactory completionof a voluntary multiple choice test.Please contact LAB -VOLT on 0480 300965 or by fax on 0480 61654for costs and dates.

Lab -Volt, Unit 6 Cromwell Mews, St. Ives, Cambs PE17 4BH, England


1 1 1 ( IItU\ICs,E 1111t1 1 ss 410121 11

New-wave architectureThe performance of traditional bus -based computer systems is

limited by the bus itself. The new architecture makes all thedevices on the bus intelligent, so that most of the activity islocal to these processors and the bus is used for data transfer

rather than program execution.

arA good understanding of systemarchitecture is important for all usersnd potential users of microsystems.

This article describes a novel approach to theproblem of how to arrange the componentsof a microprocessor system to maximize theperformance without excessive complexityand cost.

Modular computer systems made up of aseries of p.c.bs and connected via a back -plane bus were originally developed by thecomputer manufacturers as a way of increas-ing the flexibility of their systems. Thesebus -based systems allowed a wide variety ofsystems to be built from a relatively smallnumber of components, which were thecomputer p.c.bs themselves. A well-knownexample of such a bus, prominent in the1970s, was DEC's Unibus, to which some ofthe current buses, namely STE and VME,bear more than a passing resemblance.

It was the advent of the microprocessorwhich opened up this area to a wider audi-ence. The original four -bit c.p.us were obso-lete before bus standards were created buttheir replacements have spawned a diverserange of buses. The eight -bit buses haveendured longer than most pundits wouldhave predicted at the time of their introduc-tion and in fact the STE standard has onlyrecently emerged.

The first people to bring out bus -basedsystems for general use were the semicon-ductor manufacturers, whose first designscomprised a c.p.u. card, a memory card andi/o function cards, Fig. 1.

The bus was really an extension of themicroprocessor pins and it ran at the samespeed as the processor clock. The bus wasprocessor -specific and used for both pro-gram execution and data movement. Thistype of bus was very easy to implement andin general there was no contention for theuse of the bus, the single c.p.u. being alwaysin control. The bus was limited in the sensethat once the system ran out of power, thatwas it; there was no easy way of increasing it.

MULTIPROCESSOR SYSTEMS

The next major advance was to modify thebus so that more than one processor couldwork with the same memory and i/o. Thiswas achieved by adding some arbitrationlogic to determine which device had access

DAVID HUNT and KEITH HODSON

DESIGN PHILOSOPHY

Software concepts have formed an important part of the'new wave design philosophy. Insoftware terms, the language mils at the top level with the hooks into the operating systembelow it The operating system itself calls software modules which control the physicaldevices themselves. In standard VME systems, many of these modules are charged forseparately or else the system engineer has to write them. In the 'new wave' approach, thehardware modules are intelligent and the software is an integral part of the module. It is as ifwe had a 'hardware operating system'.

Figure 1. The old pioneer: This is a simple system n which the bus is an extension of themicroprocessor pins. In some designs the microprocessor address and data lines weretaken directly onto the bus without any intermediate buffering.

Disc Video I/0

Figure 2. Multiprocessors: The performance of a system can be increased by adding asecond processor to the bus. A bus arbitration unit determines which c.p.u. has access tothe bus.

to the bus. If, for example, a c.p.u. needed toaccess bus memory, it had to gain control ofthe bus first. This extra delay causes what isknown as a 'wait state' in the c.p.u. and slowsit down by typically 10%. In fact, the abilityof a c.p.u. to handle wait states is fun-damental for processors in multiprocessorsystemsAThe alternative is to stop the c.p.u.clock temporarily). Adding a second proces-sor to such a bus system did not result in acommensurate increase in performance.The main reason for this is that occasionally,a c.p.u. has to wait for access because the busis already in use. In this type of system, the

bus is the limiting factor in system perform-ance. Fig.2.

The local execution bus technique usesthe multiprocessor bus for data transfers buthas a local bus for program execution. Thisgoes a long way toward alleviating theproblems described, Fig.3. The problem isthat now, one has to be careful in theselection of card types. I have seen a recentlyproduced system with a c.p.u. and localexecution bus, except that, in this case, thedisc controller was only capable of tranfer-ring data into memory on the bus! Thesystem was set up with an extra memory card

671ELECTRONICS & WIRELESS WORLD

so that accessing data in this memory waspenalised by way of unwanted wait states.The local bus was reserved for the systemstacks only.

This idea can be extended to include anumber of masters, each with their ownexecution buses. The c.p.us each carry onwith their own tasks and the system bus isonly used for intertask communication andi/o accesses. It is now the i/o accesses whichlimit system performance.

To overcome the problem of i/o accesses,an i/o slave bus can be used in conjunctionwith the main system bus. One particularsolution, discussed in a recent issue ofElectronics and Wireless World*, is to put ina bus coupler from the main bus to the i/obus, which in this case were VME and STErespectively.

INDIVIDUAL INTELLIGENT SLAVES- THE NEW WAVE ARCHITECTURE

The ultimate solution for a fixed bus size is toassign to each i/o activity its own c.p.u. andits own local bus. It is now possible, becauseof the low cost of c.p.us and memory, to dothis while keeping the prices of the cardsabout the same as those of the old, non-intelligent predecessors. Each card in thesystem has its own operational software andcan therefore be used with any c.p.u. on thebus. In fact, these cards can be used toimprove the performance of the older systemdescribed earlier.

The implication for system performance isthat if many of the tasks of the system areexecuted in situ, bus activity is reduced. Itsseems paradoxical that we have increasedthe efficiency of a high performance bussystem by using the bus as little as often!

A crucial factor in deciding which bus touse for a given application arises here. Thejustification for eight -bit data buses has beenthat much of the i/o is in this format. This is

STE as an i/o bus in VME systems, by Tim Ellsmore.February issue.

Figure 4. Multiple master with global datamemory: CPUs operate independently ontheir own execution buses, using the globalr.a.m. for intertask communication. Nowthe i/o accesses on the bus are the majorcauses of bottlenecks.

true for serial data, ascii characters for videoand printers, SCSI for disc data and indeedfor CPIB protocol. If this is the case, theargument goes, most i/o operations willinvolve eight -bit transfers, so why go to theexpense of a 16 or 32 -bit bus when a lessexpensive bus will do? Unfortunately, wehave forgotten about the local intelligence ofthe i/o cards. These intelligent i/o cards canpreprocess the data in their local memories.For example, they can join together twobytes to form one 16 -bit word prior totransmission on the bus. In this way, 16 -bitbus data transfers can take place with twicethe throughput of the eight -bit systems.

Our new wave architecture system wouldcomprise the following:

Multiprocessors each with local executionbus Data bus with communication memoryand inter-c.p.u. interrupt facility Intelligent disc processor with local trackbuffer intelligent second management Intelligent video, keyboard and printerprocessor with a fifo buffer Intelligent i/o processor for analogue anddigital i/o Intelligent serial processor with fifo buf-fers XXX processor

XXX means you name it: GPIB, advancedgraphics, etc. This provides a loosely cou-

pled, open architecture providing eleganceand efficiency!

COMMUNICATION ON THE BUS

A master is a device which is capable ofinitiating a data transfer, such as a processorcard or a d.m.a. device. A slave is a devicewhich can respond to a master either receiv-ing data from the bus or putting data on tothe bus as required. Traditionally, slaveswere passive, but the new wave architecturefeatures active slave boards.Muter -master communication. If master Awishes to send a message to master B itcannot do so directly. The master addresslines are normally outputs only, so there isno way to establish a destination address forthe data in master B. Therefore, a globalram, which is accessible to all masters, mustbe used. This memory could be found on abus memory card or perhaps dual port ramon one of the masters.

Example: master A sends the string 'Hello'to master B.

A 1. Check semaphore bit is clearA 2. Write message string into message

blockA 3. Set semaphore bit (also causes irq on

master B)B 1. Master B receives vectored interruptB 2. Transfer message from local ramB 3. Clear semaphore bit

cpu.

Local bus

Localmemory

Figure 3. Local execution bus (above): Technique uses multiprocessor bus for datatransfers and local bus for program execution.

Multiple masters with local memory: Eac1 c.p.u. card can run its own program in its ownmemory. The bus is used to access the slaves including i o. Arbitration and control unitdetermines which device has control of the bus when more than one device requests it.

Master

cpu'

Disc

"aster(Du -1

Local bus

Local

Video

Masterc pu 1

Local bus

Localmemory

Arbitrationcontra

Masterc pu2

Localmemory

Disc

I/O

ti72 ELECTRONICS & WIRELESS WORLD

The ability to interrupt the receiving masteronce the message has been written to theglobal ram is essential for efficient operationof a multimaster system.

The communication ram is normal on theVME bus. The special feature is the interruptsemaphores. The interrupt vector could alsobe in the ram hence providing multipletransfer types. The standard bus arbitrationdeals with the problem of masters clashingand interrupt priority.

The example shown is parameter blockpassing. The same method can be used forany data length including single bytes.Master -slave communication. Althoughslaves have no mechanism for taking controlof the bus, they may be capable of causingbus interrupts. They are much simpler thanmasters and this is why the 10 processor,described below, is very attractive solutionin the new architecture.

The two commonly used data transfermethods used for slaves are basically thesame as that for masters.1. Using parameter ram: The parameter ramis local to the slave and may also appear onthe bus as i/o data area. It generally does notneed to be dual ported as the transfer of datais always under the control of a master.2. Using first -in -first -out buffer: The slavecan have a single byte for communication(read and write) which is effectively a win-dow into the fifo itself. A status register isused to control the flow of data.

CASE STUDY OFNEW WAVE ARCHITECTURE

A real example of the new wave architecturehas been implemented by PSI Systems of

The PSI New Wave Architecture showingVMEbus backplane, single -system c p uand the intelligent i/o processor. The i/obus is a low-cost 50 -way ribbon cablewhich connects the i/o processor to thesignal conditioning modules such as relaysand triac outputs. A second 50 -way ribboncable is used for the analogue i/o bus (notshown).

Cambridge on the VMEbus. In this system,the master is a 68000 series c.p.u. capable ofrunning a modern multitasking languageunder an operating system. Its local memorycan easily accommodate 2MByte of ram and2MByte of eprom. The VMEbus active slaveboards include a text processor to controlvideo, keyboard and printer, an i/o processorto control analogue and digital i/o and a discprocessor to control hard and floppy discdrives.

The components of this system are effec-tively asynchronous and can work indepen-dently of each other. In fact, master -slavearchitecture is parallel processing. The keyto the efficiency is that the backplane shouldonly be used for data transfers, and theindividual program execution is done local-ly. The master runs the controlling programat the same time as the slaves individuallyhandle their specific tasks.

Now see how the new wave architectureworks in practice, assuming that one of thetasks on that master requires a disc sectorfetch and a second task is writing to the videoscreen.

USING THE DISC PROCESSOR

The task must first gain access to the discprocessor to avoid collision with anothertask that may already be using the disc. Theprocessor will have a 'test and set' bit for thispurpose in its status byte which is read untilit becomes clear. The test and set instructionwill have left the bit set so that no other taskcan now interfere. The read -sector com-mand is now written to the disc processortogether with any data required

<read sector>, <logical sector number>.

At this point the task suspends. All of theother tasks will be continuing as normal andcan still use the VME bus to access otherslave processors. The disc processor is nowload; ng the required sector into its local dataram which can also be read from the VME-bus. When the sector is ready, the discprocessor interrupts the master and the taskresumes. The master then copies the sectorram into its own local memory and the job isdone.

Two interesting points arise from thisexample. The first is the disc access was doneas an eigh`-bit transfer but the memoryaccess was done as a 16 -bit ram -to -ram copy,the point being that the time spent on theVMEbus was very short. The second point isthat it is very likely that the next sectorrequest will follow the previous. This isalready sitting in the disc processor's mem-ory. In this case the next sector read will beextremely fast in fact at 16 -bit memoryspeeds. What we have here is the slave doingsector management.

This may sound simple and obvious but inmany systems the architectures create a


Locdmemory

1/0 t

I/O system withc pu and I/O cards

Figure 5. The i/o slave bus: The i/o is Accessed via a separate i/o bus via bus coupler (eg.from VME to STE). The i/o bus (eg. STEbus) can have its own processor(s), memory and i/ocards. In other designs, the coupler may be incorporated into one (or all) of the masterc.p.u.s and the secondary bus may be manufacturer specific. Unfortunately, suchsolutions are quite expensive, incurring the cost penalties of two backplanes and the buscoupler itself.

severe bus bottleneck by transferring thesectors directly onto the bus, either undermaster control or with d.m.a. transfer. Someeven cause the shut down of all other tasksduring the transfer.

Probably one of the worst architectures,and yet one of the most common, is wherethe execution bus and the data bus are thesame thing. Now the master program execu-tion is slowed down or stopped during a disctransfer.

USING THE TEXT PROCESSOR

Another prime area for master/slave efficien-cy is the text processor, which uses adifferent technique for communication tothat of the disc processor. The text processoruses a single -byte data channel with a statusregister to semaphore data movement.Again the activities of the slave are complete-ly asynchronous to that of the master.

Using the example of pRimr "Hello": inconventional systems each letter would beprocessed in turn. With the master/slavearchitecture the whole statement can betransferred in one go. The master can thencontinue executing its program while thetext processor writes "Hello" to the screen.This is analogous to a printer spooler. Infact, the text processor also has a printerspooler of 64Kbyte and a keyboard input.The keyboard processor stores the keystrokes in a local buffer, so providing atype -ahead facility. The master takes the firstkey from the slave buffer, if the buffer isempty, the master can request that the textprocessor interrupt the master when a keycomes in and then suspend its task. The taskrestarts when the next key is pressed.

USING THE INPUT/OUTPUTPROCESSOR

The simplest area of the computer is prob-ably the most neglected. If the system c.p.u.is running the language in a control applica-tion, there are a number of operations whichcan be performed. The c.p.u. issues com-mands along the VMEbus to the i/o proces-sor in the form

<token>, I <parameter>l<parameter2>l . . .

Because this slave is intelligent, these i/ooperations can be processed locally.

Figure 6. The New Wave Architecture: Each card on the system bus has its own localmicroprocessor and memory. Analogue and digitial i/o is controlled by the i/o processor A.so that most i/o tasks do not require the use of the system bus. The system bus is now a 1.data bus rather than an execution bus.

MANUFACTURE OF BUS SYSTEMS IN THE UK

The first bus systems were produced by the major semiconductor manufacturers and assuch they were a vehicle for the sale of their products. These products were used by systemhouses who found them wanting in some respects and as a result some went into design andmanufacture themselves.

Another group of manufacturers grew out of the add-on market These companiesoriginally developed cards for specific machines by adding extra iio to standard computersystems or PCs. A fourth group grew out of the need of some of the larger companies for largenumbers of cards for in-house use, particularly in testing and plant monitoring.

I/O OPERATIONS

Digital operationsBit -wise manipulation Immediate:a. define bit as imput or outputb. turn offc. turn ond. invert existing output statee. read external signal level

Real-time events:a. positive edge detectb. negative edge detect.

2. Byte controlImmediate:

a. output byte (write)h. input byte (read).

B. Analogue operationsUsing a 12 -hit. 12µs analogue -to -digital

6i4 ELECTRONICS & WIRELESS WORLD

converter and a 12 -bit digital -to -analogueconverter

Immediate:a. read input a.d.c. channelb. write output d.a.c. channelc. read back samples.

Real-time events:a. analogue input greater than defined

limit

b. analogue input less than defined limitc. sampling inputs over time

C. Intelligent operationsa. stepper motor controlb. linearization of transducersc. three -term control loops

D. Local i/o programsThese are completely independent i/o con-trol activities. The master can just set

parameters and monitor the activity. Theslave can interrupt for emergencies.

SIGNAL CONDITIONING

Returning to the architecture the final prob-lem associated with i/o processing is con-necting the physical devices in question, tothe i/o cards, cards generally use t.t.l.-compatible inputs and outputs with 0-10Vor ±5V analogue inputs and outputs. Thedevices, particularly power, tend to be physi-

- . ,A .,1 040,011111- . _ '

U. . tk..l.1 d..h.0 r

The New Nave Architecture showing a68000 c.p.u. i/o processor and signalconditioning modules.

cally large so that any one single height cardis restricted to eight or possibly 16 channels.

It would be silly to put a slave processor incharge of eight relays even though proces-sors now cost less than relays. A bettersolution is to construct separate i/o busesusing low-cost ribbon cable. One for say32 -digital lines and a second for 32 analoguelines. These cables could then plug in up tofour conditioning cards apiece. This schemeis actually bus -independent and as such iteliminates the need for couplers to providean eight -bit i/o subsystem to the 16 -bit VME.One i/o processor would then be in charge of32 digital and 32 analogue lines and anon -board extension gives an extra 32 digitaland 32 analogue channels. Extensions to thei/o capability of the system could be made byparalleling i/o processors on the bus.

At first glance these new generation cardsdo not look any different from their contem-poraries except for the single -height or 3Uform factor. (VME cards are more usuallydouble -height or 6U.) However, anothertechnique has been used to include theadditional features. Looking at the under-side of the cards, one sees all of the digitallogic is surface mounted. The ability to keep

the size to single -height significantly re-duces the overall system cost.

Furthermore, the i/o scheme described isactually an industry standard, bus -independent scheme that has been im-plemented in the UK in both eight -bit STEsystems as well as the PSI VME system.Taken as a whole, the new wave architectureremoves the need for 'drone' cards such asVME-STE couplers, since the low-cost i/o isnow accessible from the VMEbus.

FINALLY

The new wave architecture removes busbottlenecks of its predecessors withoutadding much to the overall cost. There is onefurther important advantage to the systemdesigner. Because the slave processors areintelligent, all of the system software relat-ing to that card is on -board. This saves thesoftware designer a tremendous amount oftime in installing the final system. Not onlythat, the slaves are processor -independentworking for a high level command/datastructure. This on -board software satisfies95% of all requirements, but to cater for theminority 5% a down -loader can be added tothe system so that system designers canwrite their own slave software.

David Hunt and Keith Hodson recentlyfounded PSI Systems of Cambridge.


TAYLOR VESTIGIAL SIDEBANDTELEVISION MODULATOR C C.I.R/3

Power RequirementVideo InputAudio InputF M Sound Sub CarrierModulationI F VisionI F SoundSound Pre EmphasisRipple on I F Saw FinerOutput any channel 47 860MHHVision to Sound Power RatioIntermodulationSpurious Harmonic Output

CC IR 3 SPECIFICATION

240V 8 Watt (available In other voltages)I V Pk PI 75 Ohm8V 600 Ohm

6MH: lavarlable 5 5MHz/Negative38 9MHz31 9M134 lavadable 33.4MHz I50us6d8 608nW 12mV1 75 Ohm5 to 1

Equal or less than 60dB40dB 18048 if fitted with TCFL1 Filter or corn

bawd via TCFL4 Combiner Leveller

CCIR 3 1 Specification as above but output level 60dBmV1000MV

CRYSTAL CONTROLLED OSCILLATOR19" RACK MOUNTING, 1u HIGH, 205mm DEEP

CHANNEL COMBINER/FILTER/LEVELLERto combine outputs of modulators

TCFL2TCFL4TSKO

2 Channel Fillet Combiner. Leveller. Insertion Loss 3.5d84 Channel Filter Combiner/Leveller Insertion Loss 3 5dBEnables up to 4 TCFL2 or TCFL4 to be combined.

TAYLOR BROS (OLDHAM) LTDBISLEY STREET WORKS, LEE STREET.OLDHAM, ENGLAND.TELEPHONE: 061 652 3221 TELEX: 669911

ENTE:It 23 ON It I'LY CARD

MODULATION METERS FREQUENCY COUNTERS R.F. TEST SETS TRANSMISSION MEASURINGTRAINING R.F. CIRCUIT DESIGN SERVICE

SIMPLY - ACCURATE TESTING

R.T.T. Systems Ltd. Enterprise House, CentralWay, North Feltham Trading Estate,Feltham, Middlesex TW14 ORXTel: 01-844 1811

QTT - I2ADIO TELEPVIONY TEST S9STEIY1S

FIELD ELECTRIC LTD. Rte3 Shenley Road, Borehamwood, Herts WD6 IAA. 01-953 6009

Official Orders/Overseas Enquiries Welcome/Order by phone or post. Open 6 days. hallday Thursday. Please ring for C/P details not shown. Postal rates apply U.K mainland

only. All test equipment carries warranty All prices incl. 15% VAT & cip unless stated

10.00 ..w/28.00. 5V 60A LI5.95 KIA47 I A 3A 1 area K1695. 028 vS 1;1015

- AV 4A 17V 500 m a 5V IA new ex -equip data L27.75- 1:'00 '... 10A 55 IA 17V iA 125 IA L3200. Gould 379 SS 4011, I.A £60.00. 50 IA PC cad regulated saw 40 watt s rk dal

. r. . . 5 1495 I .n11440400 3A meteted 18500 Metered 040V 02A '1125,.. . , A - V...,-11.45 00 V ' . A £50.00. Metered F841 are /e10 rated voltage and current

SPECIAL OFFERS . 'age regulator IM.1i11 i w',sari F L250 to 4 ... LI.30 each 1 5A 1 2V to

. m.4 220 2405 war I rte C, alone, 001001240V I at4.A 1450.00:40V lb FA 7205182A

315 New

II Merl Par lord 8405E15nd°, Voltmeter 1-1 0001.111/ farPosta, Hostel 1513531 75W positrve CHN or' Heat.*

tug 4 New

urate voltageon L1250.00.0 . p please taw

/3.00 of 11.15 earnIf Pat AnaNter A851.

1'20-1707A per winding 7400 prom New transtormerL3.50 c'p 50p 210117.00

Men Mail 1611810We State s with ophun 808511.5 IIAHOt t sari rarer A80 lor 80E10 microprocessor var.. probes etcClockprobe 6 tat data probe 11300.00 i p please ring Nest

rapst X Krushiess ra/v. IA :4W 1890 , p is / 4.4.11 P,v lard 5000A (.01- State MaNnw £63200 r p pease rag Mint

16 2716 FlItt,111, no 11 Aert 11' [`. afar, .a. FOBL1195

Hewlett Packard 675A Sweep Signal General., 101417 to 32M117 tr .,1,..fringe /460.00 i 'p please Pop Mint

Winchester 10 Meg Had .161, and s tr rigid Hatt., Hewlett Packard I97A Cantele L69.00tine removable c w th c r tr I its I. w s1 Ir vidata Ex equipment taker' tut of ricking equrpet rutwe sauna otlet guarantee 139.50 Few newWnchesters left /7500

Hewlett Pa lead 18010 Dial (tin lied Amplael 50MH), with probesnew A boxed 1460.00 L p please ring Plug in

Kadin/Pas 532 RS ITV ff 488SRI data ,.,,,,,t,,k,., 5 with. aer pont. s L16.001 opt Stale 23.4: A If Outputs. 32

Chn 250 wad deep data memory r with orb., saw e awl 111,10e twa,maniial £34500 c p please mg

Molded 75mrntaw so( Met set IFC right angle 6Asr ward Eyes 1525 ( p ;Tip New Marconi Sanders (360(10 'I Mv 'weave Sweep Osi gig. a Mainframe r with

)65 40011: RF Os' und £3.45000 c p please ring Mad16aiger SS sleeve, MM.,' step angle 1 8 max torqueWONMN prating Tonne 45ONFAN All lala a arable

L11.75 : to/ £22.00Miles High,* Irsulat.. !este, IF r0 , 'arth site 10110. /31600, uplease tong

/10 SON SS I 50 1011/ 150o/ in Sterne( Migot 700tep New. boxed L34.50 r I 50

HMI 411 0 10110 Cape gar Charge, £1.127.00 Ail 1,4ip

Wavelet, VCG Min/e1 III 1125.00Aaertylleyboad rah Lira In P511 SV 7 10,,,,,,,,,n 330 705 SO £30 50

Wavetek VCG Model 131 £125.00Wauetek 51,5 Model 142141 /ISO 00aluminum case

UK 172 Height 40 Pa, li angle ode 131.50 (WA,owes ex equr tested

Dala 10:90 PAAII hogrannter hot. 1, i v 'ata . L89500 All I it/, p Pled.' 'mg

I levilett Par Sad P.m', Mow C 14 4:10 I' Mil,rIOGH: L6500

Fluke 80IDA Digital Mtillinartet L17300

I 454 I 540411.. 0, di I _,0 r1 Delay Sweep £460x00Advance TATNA (.011144 TC3M 32M11. 14500

ektpou, ,.., .p..c p please ring

'Irann [lamer I Ilk Pulse Genetrar 13000 level For FM Ift AC Mx ro,aiivar £12600 p please ring

'.1artira, I MI619 NM 010005D( 0150500/1895

Ran & Stroud Vanable fate, EFS Power Ora nigh pass filtei00111s 10101: law pass lifer 00111/ 101111/ 130000

ALL OUR PRICES INCLUDE 15% VAT & CARR/PACKING UNLESS STATED. SAVE TIME PHONEYOUR ORDER FOR QUICK DELIVERY WITH ACCESS OR VISA CARDS

ENTERUON REPLY ('AW)

676



Mobile radio updateDeregulation and the prospect of spectrum auctions were

among the topics aired by the Mobile Radio Users' Associationat its 1987 conference in Oxford.

with delicate timing, the Departmentot Trade published its consultants'report on deregulating the radio

spectrum just a few days before the confer-ence began, ensuring that no-one therewould run short of a topic of conversation.Copies of the fat yellow volume, the YellowPeril as it was soon dubbed, were on sale atthe conference office in Keble College andquickly became as much a part of delegates'hand -baggage as the inevitable cellular tele-phone.

Some of the background to the report wasreviewed in the first session by Tony Niedus-zynski, head of the DTI's Radiocommunica-(ions Division as it is now called. He listedsteps towards deregulation already taken byhis department: the UK frequency alloca-tions table had for the first time beenpublished (and a reprint was now on theway): non -governmental laboratories wereto be appointed for type -approval testing ofradio equipment. giving manufacturers andimporters a choice of testing house (thoughapproval certificates would continue to beissued by the DTI): low -power satellite tvreception had been legalized for those whohad the necessary £10 licence (and indeedthe DTI did not for its own regulatorypurposes wish to keep any control overreceive -only users).

On the fixed links side. RD had lifted itsrule by which assignments were refusedunless the applicant could show that hisneeds could not be met by the publictelephone networks. For some fixed services.RD was even thinking of offering remoteon-line access to its database and assign-ment software: this would enable prospec-tive users to try out different scenarios to seewhich best suited their needs.

Looking ahead towards the concept ofprivate -sector frequency planning organiza-tions (FPOs) proposed by the consultants.Mr Nieduszynski spoke of moves alreadymade in that direction. "We have increasing-ly sought and used opportunities to delegatemanagement of blocks of frequencies toidentifiable groups of users," he said.

For several years, frequencies for on -sitepagers had been successfully managed by theRadio Paging Association. And very shortly,the BBC and the independent broadcastingcontractors would be assigned jointly a poolof frequencies for their ancillary services.Day-to-day management of this would becontrolled by the broadcasters themselvesthrough what would effectively be a user -FPO. Independent programme makers couldexpect to benefit from similar arrangements

WHAT THE CONSULTANTS PROPOSE

Deregulation of the Radio Spectrum in the UK s the title of the report commissioned by theDepartment of Trade and Industry in 1985 from the consultancy firm CSP International.This document examines the potential for relaxing the rules governing the radio spectrum,for transferring spectrum management to the private sector and for using market forces toensure the economically efficient use of radio frequencies.

All civil uses of radio in the UK are covered by the report, but the authors haveconcentrated on the commercially valuable ranges between 30MHz and 30GHz.

Among the report's main recommendations are the following: For substantial portions of the spectrum, the present licences should be replaced by aSpectrum Management Licence. Under this system, private -sector Frequency PlanningOrganizations would sublicense spectrum to those who required it (other than to broadcastor telecommunications operators. who would need separate government authorization).British Telecom and Mercury Communications would be given the status of Major Usersand would act as their own FPOs. Any potential user should have a choice of at least twoFPOs to approach. Bands should be considered for early transfer to the new system where the number ofindividual licensees is very large, where the band is vacant or soon to become so (e.g. BandIII). or where the present occupants have spare frequencies which they could usefullysublicense on commercial terms. FPOs and Major Users should be free to determine their range of services and chargingstructure. Spectrum Management Licensees might propose new technical specifications oralterations of existing ones. The DTI would refuse these only if they would causeinternational difficulties or unacceptable interference to other users' allotments. Fixed services bands between 1GHz and 30GHz should be managed by two FPOs and thetwo public telecommunications operators. BT and Mercury. Private mobile radio bands should be managed by four FPOs plus the Joint RadioCommittee (which accounts for some 43 000 mobile units in the gas, electricity and coalindustry) as a Major User. Each would have both v.h.f. and u.h.f. allocations. SMLs should be licensed in the sound broadcasting area. in accordance with the recentGreen Paper. Bands for exclusive satellite use should continue to be managed by the DTI. Thedevelopment of small -dish business satellite services in these bands should be encouraged. Responsibility for monitoring and enforcement should be divided between the SMLs andthe DTI's Radiocommunication Division. Amateur radio allocations should continue to enjoy a degree of protection, but the UKgovernment should apply pressure in international discussions to avoid increasing theseallocations or even to reduce them.

The consultants estimate the annual economic benefit of a 1MHz portion of u.h.f.spectrum at £75000 for fixed services, £1M to 4.6M for mobile services and £4M fortelevision broadcasting. Radio paging, with its capacity for extensive re -use of frequencies,rates much higher. These figures, they believe, indicate the advantages to the economy of are -allocation of spectrum.

Deregulation of the Radio Spectrum in the UK is published by Her Majesty's StationeryOffice at £9.50. The body of the report consists of 182 pages and there are six appendicescovering cost analyses, capacity requirements, a summary of spectrum allocationprocedures in the United States. and a review of literature.

Comments on the report should be sent to the Spectrum Pricing Secretariat, Room 305.Waterloo Bridge House. Waterloo Road. London SE1 8UA.

a little later; and discussions were in prog-ress with other user groups, including thewater authorities, local government and theLondon courier companies.

For existing licensees, policies were beingapplied much more flexibly to take accountof local circumstances: for example. facili-ties such as talk -through and reverse -frequency working were being granted.

A major piece of deregulation soon to takeeffect would be the exemption from licens-

ing of a wide range of low -power devices.including radio microphones, garage dooropeners, toys, security alarms, baby alarms.and alarms for the elderly. Some 25 000existing licences would be swept away by themeasure, which was to cover the inductionbands, telemetry and telecommand bands.including 49MHz. Also exempt would hewidehand alarms on 48MHz: the DTI hopedthat this deregulated slot would provide anopportunity for British industry to flourish.


OPPORTUNITIES

Several times Mr Nieduszynski returned tothe theme of creating opportunities. It wasthis principle, he said, which lay behind hisdepartment's thinking in looking at dereg-ulation and market forces: if the aim was toraise revenue for the Treasury or to cast offthe Department's own responsibilities, hehad not been made aware of it.

The question was how to increase oppor-tunities substantially without doubling RD'sstaff. And he reviewed some of the ways inwhich the current licensing system fell shortof perfection.

One failing centres on the operator who isinefficiently using spectrum which is in highdemand by others. He has no incentive atpresent to do other than use the cheapestand possibly most spectrum -inefficientequipment, since he gains nothing by relin-quishing frequencies. He cannot sell orsub -license unwanted spectrum. And if helets Waterloo Bridge House hear of hisposition, he risks forfeiting the frequencieswithout compensation. The licensing autho-rity could require him to buy more efficientequipment: but it had no meary of judginghow much extra cost the scarcity of spec-trum warranted.

Other problems for RD included difficultyit had in judging which of its queue ofapplicants offer the schemes with the bestchance of economic or commercial success;and the lack of incentive at present forseeking new ways of exploiting the spec-trum. Most people expected to be told thatno spectrum was available. And the user whohad been given frequencies for one purposebut wanted to use them for somethingdifferent risked losing them to someone else.

Mr Nieduszynski outlined possible ways ofreducing this rigidity, many of which werediscussed in CSP International's report.

One approach designed to increase ex-ploitation of the spectrum was to license twoor more franchisees to exploit the same pieceof spectrum, as is the case in the USA withfixed links. The user would then have thechoice of organizations able to provide himwith his assignment.

Another approach, requiring the use ofnew technology, was the currently -proposedPrivate Advanced Radio System (PARS).With this, many users could have access tothe same spectrum without interference: theequipment itself would select a free channel,and no user would have a pre-emptive rightto any particular frequency.

Later on, it might be possible to do awaywith all controls on certain bands (60GHz,for example) where it was unlikely that userswould cause interference to each other.

But Mr Niedusynski reminded delegatesthat the report did not necessarily anticipatefuture policy: the Government had an openmind on these issues. It had asked to receiveviews and comments by 30 June.

A DEREGULATING ENVIRONMENT

To start off the debate, the conferenceorganizers had arranged three presentationsto set out the pros and cons of deregulation.

First came Michael Kennedy from Motor-

ola Inc. of the USA, to give a picture of life ina deregulating environment. A .series ofFederal decisions since the 1970s hadbrought a considerable degree of privatesector control to mobile radio and hadproved very successful, he said.

Frequency co-ordinators designated foreach service handled most of the administra-tive routine in issuing licences. They proces-sed each application, dealt with technicaland other issues and were allowed to chargereasonable fees. Since co-ordinators wereresponsible for post -licensing problemssuch as interference, they had an incentiveto get things right first time.

Matters of overall policy were still dealtwith by the Federal Communications Com-mission, which continued to represent theUS's international obligations to the ITU.

There were now some 9M private trans-mitters in the US, said Mr Kennedy, andderegulation had created a very healthyclimate. It had brought more services forbusiness, especially in the fields of data andpaging, lower costs, technical innovationand many direct and indirect public benefits.

A controversial proposal now before Con-gress was for frequency auctions. Radiousers would file their licence applications inthe normal way, but the fees would bedetermined by the auction. An annual re-venue for the government of some £350Mwas though possible, and Congress wasnaturally interested. Public safety services,radio amateurs and mass media were ex-cluded from the proposal, though some feltthat tv stations ought not to be.

Motorola's fear was that auctions couldinhibit the introduction of new technology;if frequencies began changing hands .veryrapidly, future planning would become veryuncertain.

. . . OR CENTRAL CONTROL?

Arguing the case for central control of thespectrum was Jorma Karjalainen of theFinnish PTT's radio department; though headmitted (to laughter) that some of the areasnow being deregulated in the US had neverbeen subject to regulation in Finland.through lack of regulatory manpower.

The spectrum was a limited natural re-source, he said. Central control offered theadvantages of consistency of policy, econo-mies of scale important to a small country,concentration of scarce expert resources,and the ability to maintain up-to-date know-ledge of spectrum usage for forecastingfuture trends.

Summing up the arguments, John Car-rington of British Telecom Mobile Com-munications said he believed the regulationissue was a bit of a red herring. The propo-nents of both viewpoints were moving to-wards flexibility and the accommodation ofnew technologies.

Under the proposed system, he said, theidea was that RD would withdraw to a role ofrepresenting the UK at international foraand ensuring that FPOs' allocations com-plied with international regulations.

But it would presumably be necessary togive each FPO an allocation in each band;and for two FPOs, the inefficiencies this

would create might be an acceptable over-head. However, as the number of FPOsincreased, this overhead would quickly be-come dominant. "By opting for spectrumpricing as well as deregulation", he said,"one is not so much throwing out the babywith the bathwater as selling the bath withthe baby in it." A flexible approach thatencouraged redeployment of frequencies,rather than a free-for-all, was what hewanted.

British Telecom, as a major spectrumuser, is an obvious FPO candidate; and aquestioner afterwards asked Mr Carringtonwhether his company could be sufficientlydisinterested to act as an FPO on behalf ofothers. If there were two FPOs of equalstature, Carrington replied, effective com-petition would arise. Pressed by anotherspeaker who wanted to know whether BTmight turn away applications which mightharm its own business, Carrington said thatsuch worries could be ignored: colleagues inBT saw it as against their own interests to actin such a way. Another voice commentedthat spectrum pricing would not encouragebetter use because BT could afford to payhigh rates. John Carrington replied that ifpockets were deep enough the spectrumcould be sterilized, and this was one of thepitfalls of deregulation. But BT had alreadydiscussed certain areas of spectrum which itcould release for others to use.

In a later open -forum discussion, MikeCoolican of RD was asked about the reduc-tion in strength of the Radio InvestigationService proposed by the report, since manyusers might expect interference to growrather than diminish. Coolican said thereport envisaged that each FPO would lookafter its own patch of ground. Unless Parlia-ment gave FPOs policing powers, decisionswould be enforced by contract law as in theUS; though this, he added, could become alawyers' charter. Otherwise, RIS would haveto get whatever strength was needed.

The impression given during coffee -

breaks was that many delegates thoughtCSPI's package of proposals unpractical intheir present form: the report might bestrong on philosophy but the technicalissues affecting mobile radio had not beenthought through. A worry expressed by oneradio network operator concerned how in-terference problems might be resolved. Atpresent, frequency conflicts can be dealtwith quite simply by moving a channel ortwo following discussions with RD. But ifrival FPOs were involved, each might blamethe other and nothing would be done.

BAND III

Mobile radio's other hot topic of the momentis Band III radio, for which spectrum re-leased by the closure of the v.h.f. televisionservices is being reallocated. Martin Cain ofRD's frequency planning unit outlined someof the difficulties with this band, whichcertainly sounds a nightmare. Since tvbroadcasting continues to occupy Band IIIboth in Ireland and in continental Europe,interference must be strictly controlled.Protection criteria have been agreed withthe administration in France, Belgium and


the Netherlands and RD must observe themto the letter.

So far, the planners' activities have con-centrated on the middle sub -band, with basetransmitters in the range 200-208MHz andmobiles on 192-200MHz.

A formula drawn up by the CCIR is usedfor calculating the total nuisance field due tothe proposed UK stations; and it is possibleto reach the agreed limit on a given channelwith a single well -sited station in southernEngland. Because of the need to minimizeinterference around the vision carrier fre-quencies of the continental tv channels,some frequencies are no-go areas; othersnear the sound and colour subcarriers arevirtually so.

With regard to Ireland, the difficulties arealmost worse. Mr Cain said that the broad-casting authority there had regarded theUK's intentions with deep suspicion. It hadbeen talking of co-ordination radii of 700km,which would impose severe restrictions onthose areas of the UK not already subject tothe agreements with France and the LowCountries.

A further worry is the prospect of second -harmonic interference from Band II broad-casting. There is little reason to suppose thatthe many unlicensed stations lose muchsleep over this aspect of their operations.

One man who will have to cope with allthese difficulties is Alan Sheward, who pre-sented an update on GEC's national Band IIIp.m.r. network, due to open for business inAugust. The system - now named GECNational One - would offer a wide range ofvoice and data services, includingdispatcher -controlled or two-party calls, pu-blic telephone and p.a.b.x link -ups, voicemessaging, store -and -forward messagingand vehicle tracking. With its simplifiedlicensing formalities, the network would beresponsive to users; and the common signal-ling standard for all Band III systems wouldmean a wide range of off -the -shelf equip-ment. Dealings with individual customerswould be through third -party service provi-ders, except in a very few cases which wouldrequire special permission from Oftel.

Some of the practical features of trunkedBand III systems were discussed by MichaelVadon, formerly of BT and now a director ofRT Radiotelephones, the regional Band IIIlicensee for north-east England. From theuser's point of view, he explained, the readyavailability of Band III systems would be abig advantage. There would be no searchingfor base station sites, no waiting for equip-ment or for licences to come through - andso customers would buy before the whimpassed. But a drawback would be higherequipment prices than for ordinary p.m.r.:the sets were more complicated and noworld market existed for them.

MOBILE DATA

Most present-day mobile radio networks arevoice -only systems; but with the inexorablegrowth of the computer the need for datatransmission is growing rapidly. Systemsincorporating data links are welcomed byplanners because they can usually make amore efficient use of scarce radio channels.

Sweden's new Mobitex system offers effi-cient communication between data sys-tems and mobile terminals (Ericsson).

One such system is Sweden's new Mobitexnetwork, a trunked voice and data dispatchsystem operating in the 80MHz region.Following a two-year trial, Mobitex enteredpublic service last October. The system is tobe marketed worldwide under the nameMRS6000.

The network is co-ordinated via a singlecontrol channel, the same all over Sweden:by exchanging data over this channel, sta-tions may set up a speech call on one of theassociated traffic channels or transfer a datapacket. If system loading is light, packets canbe exchanged on the control channel. Aminimum system would thus consist of justtwo channels: the control channel and oneother.

Some of the trial Mobitex systems weredescribed by Giiran Berntson of EricssonRadio Systems. One is at Gothenburg har-bour, where it has apparently been used togood effect in speeding up cargo handling.When a ship is being unloaded, crane oper-ators key in the number of each container asit emerges. A central computer respondswith details of where the container should beplaced. Also linked in to the network arelorry drivers approaching the port, who giveearly warning of their arrival. The dispatchcentre can now plan their loading anddeparture automatically.

Also using Mobitex are the Swedish postoffice, whose vans now bring on-line postaland banking services to rural areas: and theregional alarm centres, which act as dis-patchers for Sweden's emergency services.Print-outs from the mobile terminals ensurethat personnel can work fast, without mis-takes and in secrecy.

By 1990, the system will be fully expandedwith 150 base stations, 60 area exchangesand 20 interlinked main exchanges.

A large data communications system nowunder development in Britain is that of theAutomobile Association, the country'slargest handler of motoring breakdowns.The AA's new operations centre at Stanmoreis the focus of its activities in the London

areaand has been in use since May, 1986.Graham Warner of the AA described the

new system, which makes use of data ter-minals carried by the area's 500 mobilepatrols. The AA's workload was increasing by10% per year, he said; and if the change todata transmission had not been introduced,the breakdown service would have becomeunable to cope by 1990. With the supersededradiotelephone system, London patrolsoften took as long as 15 minutes to contactthe base station. Only five radio channelswere available and each radio operatorhandled 35-40 mobiles.

Today, breakdown calls from AA membersare received at Stanmore by an operator whocan quickly locate each incident with thehelp of a computer -based gazetteer. Thisstores not only street names but names ofbuildings and other places of interest -including public houses, together with theirnicknames. Such information makes itpossible to cut out time -wasting 'no trace'jobs. The system now estimates how long itwill take help to reach the stranded motoristand co-ordinates the rescue operation.

Control positions are manned by twooperators, each with an interactive screencapable of displaying job details and statusinformation in 50 different screen formats.

Data communication at 1200 baud hasproved reliable in London, even where therehas been difficulty with voice. The systemuses just four of the AA's radio channels.

A second control centre at Thatcham is tobecome operational in October; and by 1990a network of 10 centres will extend coverageto the whole of the UK. The AA is nowlooking for terminals with improved facili-ties and price -performance for the remain-der of its 3000 -vehicle fleet.

RADIO TELESWITCHING

Alan Dick of the Electricity Council providedan update on the teleswitching system2 bywhich a data signal on the BBC's long -wavetransmissions is used to help trim electricitydemand to match the generated output. Thesystem, which since the meeting hasbrought the Electricity Council and the BBCa joint Queen's Award for Industry, is now


being used by most area electricity boards toreplace clockwork switches for off-peaksupply meters. A new application is in'budget warmth' schemes, by which domes-tic customers can buy electric storage heat-ing in return for a fixed weekly payment. Theoperating board uses weather forecasts todecide how much charge to provide andbroadcasts teleswi tch ing messages daily.

Now being developed in co-operation withMullard Ltd is a new metering device withcommunications facilities - the EnergyManagement Unit or Emu. This can be reador re -programmed via a hand-held unit orremotely over telephone lines. Tariff andswitching information can also be broadcastto it by one-way radio. Emus can handle upto six charging rates, allowing time -of -dayand seasonal multi -rate tariffs. Securitycodes are used to prevent tampering. For theforthcoming trials, the system will be

controlled from the area board's office by adesk -top PC, which will also act as aninterface to the accounting computer.

The trials form part of a European projectaimed, among other things, at showingwhether customers can be coaxed by specialtariffs into modifying their pattern of con-sumption and so reducing overall energycosts. Besides the 850 Emus to be installedin Britain, a further 150 will be in Brusselswhere they will be controlled over a cable INnetwork.

Another remote -metering idea under In-vestigation was to fit electricity meters witha radio device which would enable them tobe interrogated and read by equipment in anearby van. The customer's wiring andservice cable would act as the device'santenna. Trials have already been conductedin the US on a 900MHz version, by the LongIsland Light and Power Company; thoughMr Dick believed that a frequency in therange 1-3MHz would be more practical. Butwould the DTI be willing to allocate one? Asingle 8kHz channel would be sufficient forthe whole industry.

The cost of reading meters worked out at80p-12 per year, and any electronic systemwould have to match this target.

CELLULAR-THE FUTURE

Steve Temple, another member of the RD'steam, turned the spotlight on the future ofmobile radio, where international develop-ments may bring big changes over the nextdecade.

Planners, he said, had to think of theindustry's needs ten years ahead, since ex-perience showed that it took this time fornew schemes (such as cellular radio) toreach fruition. Users should get togethernow with the DTI to ensure that prepara-tions were made. Another mobile radioWARC would be needed around 1992.

Cellular radio in Britain had been a spec-tacular success, with more mobiles in ser-vice than anywhere else in Europe: 90 000new users were joining each year, comparedwith 22 000 in Germany.

For the future, European heads of statehad agreed in December that there should bea common standard for a future cellularsystem and there had been a directive from

Gasmeter EMU.44

_ _ _ Including

_ _ electricitymeter and

Water radiometer receiver

CustomerDisplay Unit

Telephoneinterlace

Prototype Energy Management Unit, orEmu. The customer's installation can belinked to an extensive communicationssystem controlled by the area board.

Brussels to keep channels available.There was complete unanimity in Europe

that a narrow -band t.d.m.a. system was thebest technical solution. Thirteen adminis-trations felt able to go forward with thissystem for 1991 implementation date, withonly two (France and West Germany) hold-ing back. [Since the meeting, those coun-tries have agreed to support a modifiedspecification containing features of theirown proposals.] At least three large Euro-pean markets would have to be available in1991 for the system to be a success; but UKmanufacturers would have a chance to be-come world -class contributors to it.

SATELLITES

Other centres of activity for planners in-cluded a new European radiopaging systemfor the mid -1990s and a so-called aero-nautical public correspondence service. Thislast would give businessmen global com-

BBL,Message

assembler

Packetswitchingsystem

munications by portable telephone whereverthey went. Satellites like those of Inmarsatwould handle in-flight calls, though directground links for the heavily -populated Euro-pean area might be cheaper. Mr Temple,whose hotel in Brussels had just chargedhim £70 for putting through a brief call toFlorida, evidently felt strongly about this.

The introduction of satellite systems forglobal mobile radio is not as far off as it maysound, as delegates heard in a presentationby John Norbury, head of the radio commu-nications research unit at the RutherfordAppleton Laboratory. Interest in the idea, hesaid, had been stimulated by the ATS-6project of 1974, with its 860MHz communi-cation transponder.

Later experiments with geostationarysatellites - such as the Canadian M -Satproject - had been encouraging, but thisclass of orbit brought a considerable costpenalty for countries at moderate latitudes.To avoid the need for a tracking system,mobiles had to use omnidirectional anten-nas; and in North America a 15dB marginover the free -space signal loss had beenfound necessary because of the satellite's lowelevation. A much greater margin would beneeded in cities. Link margin for satellitesystems was expensive: one rule of thumbreckoned it at 11M per dB.

An alternative scheme, with which thespeaker had been involved, was for a systemusing an inclined Molniya-type ellipticalorbit: such a satellite would appear to hangoverhead for perhaps 8-12 hours at a time,avoiding the problem of blockage by build-ings. With a constellation of three satellites a24 -hour service could be provided.

References1. Trunked mobile radio in Band III, by P. J.Delow: Electronics & Wireless World December1986, page 51.2. Broadcast radio -data, by D. T. Wright and S. M.Edwardson: Electronics & Wireless World Novem-ber 1986, page 63.

Conference papers are available from the Mobile RadioUsers' Association at £25 a set. The association's newaddress is 28 Nottingham Place, London W1M 3FD. Tel.01-400 1518.


"I've solved the problem, Charles. Livingston Hirecan provide everything we need on rental terms".

8655 companies have already discovered the benefits ofelectronic equipment rental, and the number grows daily.The Benefits of RentalThe comparative cost of renting canreasonably be estimated at 10% of the purchaseprice per month for short-term periods of up tothree months, falling to about 6% per monthfor a period of one year or more.Very often rental is the easier and moreconvenient way to acquire electronicequipment, the financial arguments beingonly part of the story. There are numerousoccasions when rental is the undisputed, if notthe only, solution.Remember, with rental you pay only while youuse the equipment. With ownership you pay allthe time.

* EvaluationWhen a manufacturer introduces a newelectronic product and you want simplyto evaluate thoroughly before purchase- RENT.

* Peak DemandWhen you have a peak load or majorre -calibration problem and you needtemporarily to augment your ownequipment - RENT.

* Panic needWhen you have an emergency situation,a crash project or a plant/equipmentfailure - RENT.

When renting you incur: * Defined Short-term need* No maintenance or repair costs When you require something special for a* No interest charges specific short-term project, contract or* No calibration downtime assignment - RENT.* No provision for replacement

And you can have the equipment:* Returned the moment you finish with it* Replaced if it becomes faulty without any

cost* Changed if it becomes obsolete or

technically unsuitable* Returned during your works closure

In addition you can:* More easily allocate costs to projects,

production programmes or plants sincethey are fixed and known precisely inadvance* optimise taxation

* Low utilisationWhen you have a tight budget andutilisation is below an economic level toallow purchase - RENT.

* Long lead timeWhen you are given protracted deliveryperiods from a manufacturer but yourcontract or project must not be held up -RENT.

* Uncertain use patternsWhen a contract specification is initiallyuncertain and you are unsure whether ornot to include equipment in your capitalbudget plans - RENT.Ring or write to Europe's No. 1 inelectronic equipment rental for a freecopy of our 164 -page product catalogue.We've over 16,000 items on inventory.Or ask for our booklet "The Case forElectronic Equipment Rental". We'rehere to help - whatever area you're in.

Livingston Hire01-9778866

Livingston House, The Rental Centre, 2-6 Queens Road,Teddington, Middlesex TW11 OLB.

NORTHERN Tel: 061-998 7900 SCOTTISH Tel: 0506 415757


MARCONI TF2371 200MHzSPECTRUM ANALYSER

.Y# &

RALFE - ELECTRONICS10 CHAPEL STREET, LONDON. NW1

TEL: 01-723 8753/724 8074

EST35

YEARS

JOY:- 200MH, frequency range 0 100 6 5Hz resoiution 100db displayedCynami< range Inbuill tracking gen 8 counter MINT congtan Unusedorce recent cafityafion ION S 111000

synthesized signal generators AylOnn's model 1 5.1040M14, wdh'of qwing options I Extended FM bands. - 2 VOR ITS capabdttyPu se moduiator Plus GPIB IMLP with 015 e 0001 Our price as new

"ifirior :nth ru guarantee £2500

TF2006 AM FM Signal generator 10 1000MHzTF2011 FM Signal generator 130-180MHzTF2015A. I AM FM Signal generator 10-520MHrTF2016A VHF AM FM Signal generator with 2173 lock -boxTF99545 AM FM signal generator 1 5.220MHz2017 AM FM sognai generator 0 01.1024MHz Superb spec

(950(325(600C850(195

08 000TF2170 digital synchronizer (tor 2002 set&si (400TF2300S modulation meter 35-1000MHz AM FM £495TF2303 Modulation meter 2 5-520MHz AM FM C325TF1313 RCL Universal Component Bridge 0250TF1245 0 -Meter wet oscillators 1246 and 1247 (500TF1245A r Meter 12468 1247 (550 (250 (150TM4520 ..d inductor set (250TF893A .cwe, meter 110W10W tsd (75TF1020 A .0 250MHz RF power meter (75TF1152 A .0 250MHz RF power meter E75TF2604 -ic muttfilunction meter (175TF2430 . Frequency counter (95TF2807A -Tuna*" tester (6002821 ' 'Li analyser (8502833 .ra vie monitor 05002829A s.rnulaior (12507F7356 20MHz ieveT osciiiator (1100TE2167 Or ampere, 11 115 C450

(250TF2092C 24507F2SP0TF216.

C750(100

is now available tor all owns or equipment costing £1000 or more'For an additional 10°. of purchase pace we can one, a comprehensivepans and labour warranty for a lull year and we still guarantee tounaer-cut our cosest competitor, Cenificates of calibration to &Pon&standards traceabirrty are available upon request for certain itemsPlease er es bore you

.TEST & MEN EIMEMARCONI TF2502 RF Wattmeter 10W tsd 1GHZMARCONI 2435 2GI-17 8 drgrl frequency counterGREEN 2601 Wattmeter 0 3.300W to 500MHzTELETYPE Terrnina, model 43 RS232 aceDATALAB C11905 Transient recorderTELEOUIPMENT C771 Transistor curve tracerTEKTRONIX 575 Transistor curve tracerTELEOUIPMENT 083 Oscooscopes SOMHrTELEOUIPMENT DM64 Storage scopesOSCILLOSCOPE - stock phone for best quoteBRYANS 22020 SOT Plotter A3GRUEL 6 KJAER 1402 Random nose genDYMAR 785 moduiallon meters 30-480MHz AM FMDYMAR 781 S RF power meter 1-30WGPW 7620 Telegraph i5 Data generatorAVO VCM163 Valve characteristic meterRACAL 9301 RF Voltmeter I 5GH,RACAL 383 4 -Trace display osolloscope

£450£250C250£750[250(450(275(600(250(350

fir, (250

Et 75(250(125(75

C195(400(450C175

VAL RACK) 24V DC input to 2300 50Hz output 120W Sine Wave£18S (Pew): t125 fused1

150W SOu aro wave T75106.41140 5A chargers ta5

ALL OUR EQUIPMENT IS SOLD IN EXCELLENT. FULLYFUNCTIONAL CONDITION AND GUARANTEED FOR 90 DAYS.MAIL ORDERS AND EXPORT ENQUIRIES WELCOMED. PLEASETELEPHONE FOR CARRIAGE QUOTE. ALL INSTRUMENTS AREAVAILABLE EX -STOCK AS AT COPY DATE. G000 QUALITYTEST EQUIPMENT ALWAYS WANTED FOR STOCK. PRICESQUOTED ARE SUBJECT TO ADDITIONAL VAT

80070 Pulse generator8555A Spectrum analyser oneto 40GHz400F Voltmeter t00.V 3000 4M1-1,73411311Caetbratot

4800A Vector impedance meter116028 Transistor Ileum tor 8745A116008 As above8004;1058 generator7045A KY Plotter OPt 001 ITtme-basel3556 Programmable altentiator 'GM: 0 1206355F As above but 120017m 1 ddb steps3490A Neal Multfimeler

8733A Pm modulate855319 Seereere analyare pino in 1101,0,7

[500

(2950£225(195T750£450

(225£750

(95(95450

(450TI500

TWO

I * HP1417 SPECTRSYSTEM to 40GHz ,U1111111r1111111

.4111111).11, .

SYSTEM Comprtses of type 1417 Storage mar -frame 85528 I F plug-er welland 8555A 10MHz 18GH2 i406Hz with external mixers) R F plug £6500Etcesent throughout 046514 1' centnea

HEWLETT-PACKARD 110MHz System 141Ti8552/15538 t3500

lir -rut_ sucrratrzANALYZ

. anv1 range 70db BandwidthLiscope Troth external )(Anon,

rem, aces as ne .sp,dy EPO-ELENT CALVE E750

HP8407A

With types 8412A Phase Magnitude and 6414A Polar osotay units 110MHzRecent nalibratoOn T2500


fricrokit 0536Ltd. 24 hr3

d7 4 4,16 64

74TTL 40% OFF SAVE OVER 40% PRICES SMASHED ON OURLS BC LINEAR MEMORIES

20 25 30 ON OURDYNAMIC Mg CV 11M05

20 25 30 EX -EQUIPMENT 4164 15 8820 25 90MEMORIES AND memory upped« AM6-1 RAI -20 9.90 41256-15 256K x 1 2.3920 25 .40 EPROMS 14:515 16K x4 3.30

.20 .25 40 1000's of delighted 1 ;^4 12 641(04 3.30

.20 .25 1.20 -- .100C 12 IM BIT CMOS 32.00

.20 .29 55 customers.. t.1 1,7 *".! 35.00

.20

.20

30 .20

292927

45406518

GUARANTEED UVERASED AND TESTED

c.1t, ...K C 1.50:132 4K.0 1.50

STATIC NAM 'V NMOS

' 1.501.80

32 .20 35 .90.1764 BK08 1 20 STATIC RAM 5V CMOS

42 .49 5027128 161(x8 1.75 1.40

51 AO

73

.2529

4545

All taken ft' rti 4

. -

1 70240

74 .20 .39 70T oatd5

14.5085 59 s" - -

RP .20 .49 4000 SERIESFLOPPY DISC

LPH5TMS 5V NMOS2.7018 CONTROLLERS 2.65.49 Ie

19 00 2.45.47 3319.00 2.70.49 18

3314.26 3.75

.22 .49 .21 PROCESSORS 8.208.40

138 .40I39 .40

.49.49

21

182.501.50 I PP( 1510 W CMOS

153 .45 .59 i 18 3.75 6.50154 .85 33 4.60I . .40 .55 72 IC SOCKETS 2.70

32 10 5.20.55 .55 l 32 .12 9.70

0.1 .26 16.55

64 .55.55.55 .34

65 AO66 .60

.75

.60

.2818

MICROPROCESSORS1.60 FREE

74 .40 .55 .85 5.00 POSTAGE75 .55 .55 .35 2.60.

93 .6094

.75.28 6.90

ORDERS OVER £25* * * * HIGH TECH ****240 .5650 .89 ORDERS UNDER £25 ADD244 .65245

.89 NEC V20 UPD70108 ci P&P ADDS5% VAT257 .5080 .5955

8088 to speed IBM PC 10-40%replaces upEXPORT WELCOME273 A5 .89 16gh speed address calculation Ito hardware

365 .40 .44 Par compatible with 8068 £3 P&P367 40 Superset of 8088 instruction set

373 AS .95 1."' P.".e CM°S FREE374 .65540

.95

.65

8611fx V20 ITPD701138-8 6I3.508Mlfs V30 UPD70116-8 L14 SO CATALOGUE

643 1.25 * * * *SPOTLIGHT* * * * WITH FIRST ORDER

ORDERS DESPATCHED SAME DAY BEFORE 3 30pmDEPT (W7), 18 COLDORMEADOW AVENUE, CORBY. NORTHANTS NN I8 9A)

VersatowerA range of telescopic towers in staticand mobile models from 7.5 to 36metres with tilt -over facility enablingall maintenance to be at ground level.

Designed in accordance with CP3 Chapter V, part 2,1312 for a minimum wind speed of 140 kph inconditions of maximt.m exposure and specified byprofessionals world wide where hostileenvironments demand the ultimate in design, qualityand reliabilitySuitable for mounting equipment in the fields ofCommunicationsSecurity surveillance - CCTVMeteorologyEnvironmental monitoringGeographical survey3efence range -findingMarine and aero navigationhoodlightingAirport approach lightingFurther details availatle on request

z4,STRUMECH ENGINEERING LIMITEDPortland House. Coppice Side. BrownhtllsWalsall, West Midlands WS8 7EX, EnglandI elephone. Brownhins .0543) 452321Telex. 335243 SE L.

&ere,

I alb

ENTER I I ON REPLY CARD

682


ELECTRONICS Sr WIRELESS WORLD

ICF7600Dtest signalsfor v.h.f.receivers

Sony's ICF7600D is a handheldbroadcast receiver with synthe-sized shortwave tuning underthe control of a dedicated micro-computer. Here's how the localoscillator signal and its harmo-nic can be used as an accuratecalibration source for two andfour -metre receivers without anydirect connection.

The 1CF7600D uses a variablefirst local oscillator operatingabove the selected frequency andthis is provided by the synthe-sizer with considerable preci-sion. Suppose that you wish toconfirm that a two -metre receiv-er is tuned to channel S20(145.5MHz). Switch on theICF7600D receiver and select16.905MHz. Hold the ICF7600Dclose to the antenna. Thesquelch should lift and a strongc.w. signal should be indicated.

This is because the secondharmonic of the I.o. falls withinS20. Table one shows some of theS channels and their correspond-ing settings.

Two -metre channel AM setting

S14 16.830S15 16.840S16 16.855S17 16.865S18 16.880S19 16.890S20 16.905S21 16.915S22 16.930S23 16.940

Formula one enables a frequencyand its setting on the ICF7600Dto be calculated. Errors canoccur since the test signals variesin 10kHz steps whereas the Schannels are in 25kHz steps.However any variation in theICF7600D will cause the testsignal to favour either the odd -numbered S channels or theeven -numbered S channels. Thismay in turn be checked against atwo -metre repeater output.

The five -line program enablesa microcomputer to calculatethe corresponding a.m. settingsbetween 112 and 171MHz. Thisallows marine band and air -bandreceivers to be checked.

FFEEDBACK;10 DEF FN F(X) = X/2 - 55.84520 PRINT Frequency'.

" ICF7600D " : PRINT30 INPUT " Enter Frequency

MHz " ; f40 PRINT f , FN F If)

50 GO TO 30

a.m. setting = 1/2 - 55.845 (1)

In the case of four -metre receiv-ers the fundamental I.o. is used.This enables 5kHz steps to bemade and the formula for obtain-ing the a.m. setting becomes

a.m. setting = f - 55.845. (2)

The procedure for four -metretests is otherwise indentical, forexample, the ICF7600D would beset to 14.415MHz a.m. to cali-brate 70.26MHz.

Other settings correspondingto frequencies from 56 to 76 MHzcan be obtained.

This unusual application ofthe ICF7600D has been of greathelp for setting up receivers andconverters in the absence oftransmissions. The reader is leftto work out how a 70cm receivertest signal can he generated.Mike MucklowStony StratfordBucks

Betrayal ofscience by

`modern physics'We can classify discipline as

ranging from hard to soft: fromphysics, engineering, chemistry,biology: through sociology.psychology: to geography, his-tory, literature, religion. Thehard disciplines are described as'science'.

In a soft discipline. a model,theory or fact is still of value evenif it is imperfect, flawed.

The definition of a hard scien-ce could be that it is capable ofsustaining a perfect, true, model.theory or fact.

For prestige reasons, the softsciences - sociology and psycho-logy - try to take on the mantle ofthe hard sciences by using 'scien-tific method': a method of arriv-ing at rigid, 'true', facts, modelsand theories. They do this inorder to gain access to the pre-stige and funding (NASA -type)that the hard sciences command.So we see subjects trying to moveto the left, from soft to hard.

Unknown to the soft sciencecareerists, struggling towardsthe left, the position of theircolleagues at the hard, physicsend is uncomfortable. This isbecause if a theory can be exactlytrue, it is also brittle: morevulnerable to complete overturnby new developments than is asofter, imperfect theory. Nowcareer advancement is, if any-thing, a soft subject, not a hardone. So for career reasons, atraitor group in physics has de-veloped a soft discipline called'modern physics'. These career-ists betray science by softeningtheir discipline and so stablizingthe theoretical status quo andwith it their career status quo.

An individual's career in hardscience is brittle, because it is

based on more absolute, there-fore more brittle, theories andmodels. He then makes his posi-tion more pliable. and his statusand career more secure, bysoftening the brittleness of hisdiscipline. In doing this he be-trays his discipline in order toprotect and further his career.

'Modern physics'. a bastardpseudo -physics, is a soft disci-pline which has been developedby career physicists unwilling torisk a brittle career in hard sci-ence.

Meanwhile, the soft sciences(sociology and psychology)trying to obtain the prestige andfunding of the hard sciences arenot fearful of this brittleness. Inany case 'modern physicists' aretelling them that physics is soft.

The sign posts on the roadfrom physics to modern physics- from hard science to soft- are:uncertainty: (wave -particle)dualism: confusion of observerwith observed: relativity: and theuse of statistics and probability.Paradoxically, one of these, sta-tistics, also signposts the oppo-site march of the soft sciencestowards the hard.Ivor CattSt Albans

Oscillatoramplitude

stabilizationIn the good old days a filamentbulb or an n.t.c. resistor wasused for amplitude stabilizationin Wien Bridge and phase shiftoscillators. However, the output

amplitude, though stable, wasoften unpredictable and tendedto change with ambient temper-ature. These days. active controlcircuits using fets, o.t.as or otheranalogue control circuits aregenerally employed. The majorsource of distortion in these typeof oscillators is the non -linearityin the gain -control element (be itfilament or fet).

This is well-known, but thereis another factor that is generallyoverlooked. The output of thesinewave generator is rectifiedand smoothed by a low-pass filterbefore being fed to the activecontrol element. Now even if thegain control element was per-fectly linear, there would be asecondary source of non -linearity since the a.g.c. biasvoltage is not purely d.c. as itshould be but contains traces ofthe oscillation frequency itself.The conventional remedy is tomake the a.g.c. time constant aslarge as possible, but this is notthe best solution.

Theoretically, it seemed, therewas no way in which the controlvoltage could be made purely d.c.without an excessively long timeconstant. I was pondering overthis problem for a long timewhen the identity sin2x + cos -x= 1 occurred to me.

If we take the two outputs of aphase -shift oscillator that are 90°out of phase, full -wave rectifythem, feed them independentlyinto voltage squarers, and addthe resultant waveforms, we geta direct voltage proportional tothe amplitude of the sinewavesbut having no a.c. componentsin it.

Of course, this method isn'tvery elegant as analogue squar-ing chips are not exactly cheap,but it is certainly worth trying. Iam not aware whether any ofyour readers have thought of thisidea which I feel is the solution tothis problem.K. ShankarMadrasIndio

New marketsI read with interest the editorialin the April edition discussingnew markets for the UK electron-ics industry. I would like tosuggest another region whereUK and Japanese companies mayhe able to find new markets.

The countries of Latin Amer -


ica have historically traded withthe United States. but in many ofthese countries governments areemerging which seek greater in-dependence from the USA andare trying to reduce their tech-nological dependence on theUSA. Nowhere is this more truethan in the Central Americancountry of Nicaragua. whichfinds itself embargoed by the USand has turned to Europeancountries, the EEC and the Com-econ nations for new tradingpartners.

I am about to go as a Britishvolunteer to Nicaraga, to teachdigital electronics and micro-processors at the National Uni-versity of Engineering. I will beresponsible for establishing anelectronics laboratory at the uni-versity and advising local indus-try. I have over 10 years experi-ence in industry: currently I amthe manager of an electronicslaboratory within Lucas CAV Ltd.

I would like to invite readers toconsider donating equipment tothis university laboratory. Theprimary benefit to companieswould be that Nicaragua's newgeneration of electronics en-gineers would be trained usingtheir equipment. What may beless obvious is that the universityhas some 21 different nationali-ties amongst its staff. a largeproportion of whom are fromother Latin American countries.The university also has visitorsfrom all over the world: particu-larly Western Europe, the Com-econ area, the United States andLatin America. Thus equipmentgiven would be seen and used byan unprecedented variety ofpotential customers.

Any help offered will be asignificant contribution to apoor third world country and willbe genuinely appreciated. I cansupply a detailed list of the equip-ment and components requiredon request (01-743 3111 till theend of June, 01-993 5631 after).Donald Power34A Cowper RoadLondon W3 6PZ

Transistorsound

Having followed with amaze-ment the debate about 'capacitorsound' (which can be practicallynullified by using, where un-

FEEDBACKavoidable, high quality electroly-tics correctly biased and suitablybypassed) I should like to recallattention to the subject of 'tran-sistor sound.' which is more no-ticeable. less controversial, andperhaps a more rewarding sub-ject for investigation.

Most of the pundits will haveread M. Hawksford's paper oncharge quantization in bipolardevices, and the recommenda-tions for minimizing the prob-lem. This prompted a closer lookat the extent of the effect: How itcould be calculated for a givenamplifier and, hopefully, re-duced to negligible levels.

A few calculations showed thatcharge quantization is a propertyof small alternating currents andthat it would present problemseven to a perfect current -drivenamplifier. Given that the chargeon the electron is 1.6 x 109coulomb, it is immediately ob-vious that no bipolar amplifiercan resolve a signal smaller than3.2 x 1019A per Hz (i.e. oneelectron per half cycle). At 10kHzthe smallest a.c. that can flow is3.2 x 10 15A. the only conceiv-able waveform of this currentbeing rectangular. This currentrepresents the threshold of fuzzfrom both the logical and auralpoints of view.

For any current -driven ampli-fier (i.e. bipolar input) thesignal -to -fuzz ratio at the inputwill be 20logI1m/3.2 x 10 151 dBor a little more conveniently20log[3.12 x 1014 1,n1 dB. Alter-natively the ultimate signalresolution (u.s.r.) is equal to3.321°0.12 x 10141,n1 bits at10kHz referred to a given inputlevel, lin (A r.m.s.).

For any amplifier it is onlynecessary to calculate the actualcurrent (ignoring external loadresistors etc) flowing into theamplifier at, say, 5cm/s recordedvelocity for phono inputs or 1Voutput for power amplifiers.

For example consider a typicalop -amp phono preamp:

Open -loop gain (10kHz) 6000Open -loop input

resistance 100k12Closed loop gain 10

Cartridge output (5cm/s15mVPreamp output 50mVDifferential input (50mV/

6000) 8.33µVInput current (8.33µV/

1001d2) 8.33 x1011A

(This is the net current flowinginto the amplifier itself. not the

cartridge load resistor.) Thus

s.f.r. = 20log (3.12 x 10" x8.33x1011(i.e. 88.3dB

u.s.r. = 3.321og (3.12 x 1011 x8.33 x 10 11(

i.e. 14.7 bits at 10kHzref. 5cm/s.

Until bipolar input stages areredesigned to allow higher inputcurrents it seems that it will benecessary to use valve or f.e.t.input stages for good signal re-solution.Roger C LowryChristchurchNew Zealand

RelativityProfessor Michael Butterfield(Feedback February 87) believes"that without space which per-mits geometrical shape andmovement, our very existencewould have no meaning". This israther a strong philosophicalpoint of view which implies thatas a priority we must have"space" to begin with so thatthings can happen! Moreover, wehave also assigned to this strangespace many properties so that DrH. Aspden is, therefore, morethan justified to fill it with anether if by doing so the explana-tion of physical phenomena be-comes easier as well as moreinteresting and palatable!

It is not my intention in thisbrief letter to comment on the"Relativity Simplified" articlebut to emphasize that one of themanifestations of matter in theuniverse implies (create) the"idea" of space. Without the pre-sence of matter there is not sucha thing as "void" or "space" andconsequently geometrical shapeand movement is unthinkable.These aspects can only be direct-ly associated with the energy andforces belonging to material ob-jects. Equally, we cannot gobeyond the world of materialobjects to look for an abyss of aninfinite space. We can onlyconsider the existence of a"medium" between any two ob-jects that are acting upon eachother (be it electromagneticallyor gravitationally). We must.therefore. be concerned with thestudy of this limited and finitemedium with respect to theseobjects and avoid at all costextending our system to involvewhat is logically inconvceivableand in the process get lost in a

forest which neither Cod norNature had ever created.

Finally, universal time is farfrom being an outdated New-tonian concept that had to bethrown out of the window like adead corpse before the arrival ofthe respectful Einsteinian worldsystem at the front door. Grantedthat, for the sake of practicalnecessity, we are forced intoaccepting, for example, our ownearth frame of reference to bestationary in the universe (i.e.zero energy level with respect toabsolute motion, this onlyleaves us with a clock that canread local but not universal time(for the simple reason that so farwe are unable to detect, andtherefore correct for, ourmotion with respect to that pointfrom which everything hadstarted). If it is possible to arriveat this "common time" in a fu-ture theory, then we shall be in aposition to do without measur-ing rods, forget about the con-cept of simultaneity as well as thebedside story of the paradox in-volving the far space travellingtwins. I expect many so-calledRelativists would then be onlytoo happy to throw some of theirown cherished and over-protected hypotheses of Ein-steins's Special Relativity out ofthe window as well!M. Zaman Aki IAl-ThubaeyaKuwait

`Computers,language and

logic'I read the article entitled 'Com-puters, language and logic' by A.Medes but could not understandthe purpose. I was unsure whilereading it so when I got to theend, applied the objective test -see if I could summarize what itwas about. I couldn't really writedown anything concrete. Allud-ing to something? Mathematicsof higher degree circuitry? Thisis the sort of thing that I havebeen arguing for to reinstatecausality.

Other than this there wereoccasional patches of compre-hensibility but no overall coher-ence. The logical problem "I am aliar" was dealt with as a feedbackprocess in a logic inverter tosimulate the sequential processin our conscious awareness,


accepting one idea then theother, then back again.

Is the concept of causality stilltreated with contempt or are youbecoming educated to under-stand your own mental proces-ses: not to have double values, inengineering practice (causalityrules the machine, intuitiveknowledge) and in theoreticalmodelling (causality appears tovanish in asymptotic equilib-rium formulae).

In the example here, it is pre-sumed there is a propagationdelay to explain oscillation, thelogic unable to 'decide' on aconsistent certainty.

How would you explain thetheoretical inconsistency if yourephrase the problem, replacingthe logic gate with an analogueamplifier and used the 'op -amp'formula for negative feedback?

The op -amp formula does notpredict oscillation simply be-cause this intuitive informationis not programmed into its de-rivation which assumes, falsely.that stable equilibrium can existfor the feedback currents.

If causality is assumed withpropagation delay, we use itera-tive analysis, the feedback pro-cess generates a power series ofterms (voltages) which IF it con-verges produces the op amp for-mula as its asymptotic form.

The instability between 0 and1 states does not appear in theop -amp formula which passesthrough the logic value of 1/2 (seemaths textbook 'DivergentSeries' by G. H. Hardy).

The author A. Medes seems tobe struggling for an idea: "Thecalculus of logic can be used todescribe some simple circuits,(no feedback)...but it is totallyinadequate if we require rigorousmathematical description ofother types of circuit". Logic saysnothing about physical reality.Logic is merely a low -noise in-formation storage medium - amedium for storing informationor physical intuition derivedfrom experience.

The required idea is causality.modelled by discrete elementanalysis. Interactions are de-scribed by iterative processeswhich might converge to anasymptotic limit under certainconditions of the feedback in-teraction. The asymptotic limitis called, inappropriately, the'generating function' for thepower series of the iterative pro-cess.

FEEDBACKJustification for the use of the

surd V-1 is: logical self -consistency. It needs no more'meaning' than its definition:when multiplied by itself it gives-1. In all complex formulae thereal and surd elements remainlinearly independent of oneanother because they cannot becombined in arithmetical cal-culations until all surds aretransformed hack to reals again(in some 'real' invarient).

In modelling physical situa-tions j = V-1 arises in asympto-tic formulae (of circular func-tions) when we assume equilib-rium can exist for the amplitudesof sinusoidally varying re-sponses.

The mathematics of complexnumber algebra is neat but hidesa lot of physical assumptions thatmay not necessarily be valid. Sodon't he fooled by superficialitiesof appearance.P1 RatcliffeStevenageflats

Time and spaceI enjoyed reading Scott Murray'sarticle "If you want to know thetime..." but searched in vain forthe rider "ask a relativisticpoliceman". Can it really be thatclocks at the pole and at theequator can cooperate to provethat Einstein was wrong?

Such a proposition is out-rageous and I have it on goodauthority. The editor of PhysicalReview Letters has drawn myattention to an experiment* re-ported by NASA. It appears thatin 1976 the NASA -SAO rocket -borne redshift experimentproved that the theory of relati-vity was correct and that over a10.000km range from the Earthlight speed was the same in oppo-site directions within 3 parts in abillion. If this is true, then, as anantirelativist, I am defeated andScott Murray should hoist thewhite flag as well. No longer canWireless World entertain us byencouraging debate in this excit-ing arena of 'relativity'.

It wold indeed be sad if Wire-less World followed the exampleof Applied Optics. The editor ofthis journal. published by theAmerican Institute of Physics,had occasion to write at page 544of the March 1977 issue: 'It wasprobably unwise for Applied Op-tics ever to have ventured into

the controversial area of relativ-ity theory land the various optic-al tests for it). In that area eventhe experts carry long swordsand enjoy duelling to the death.Unarmed editors of applied jour-nals would be well advised toavoid that battlefield'.

It appears that NASA did senda stable maser oscillator intospace to test relativity. As a clock.it behaved as expected in slowingdown as it returned to the stron-ger gravitational potential in itsdescent. This is just as ScottMurray would predict. But whatabout the time dilation effect dueto motion? Well. since relativityreferences motion on the obser-ver, the speed of the rocket wasreferenced on the Earth frameand the time dilation terms weresmall enough to be ignored. Theexperiment performed by NASAhas such small residual errorthat it could be said with confi-dence that the radio signals sentto the rocket travelled at thesame speed as those sent backfrom the rocket. No evidence ofmotion through the preferredframe was found, and the rangewas 10.000km.

Now. what is fascinating aboutthis experiment is that it was amajor NASA project involvingnumerous scientists and aimedat testing relativity. It was seenas an experiment to detect mo-tion through the ether, besidestesting the effects of gravity. Yet.in the analysis the time dilationwas calculated as referenced onthe Earth frame, whilst the re-sulting equation was used toestimate motion relative to thepreferred frame. Could one reallycredit such an error? When thetime dilation formula is refer-enced on the preferred frame theresulting equation contains noterms which would allow theanisotropy to be tested. Theeffects cancel out completely.making the test completely in-consequential so far as detectingour motion through space is

concerned.Such is the arena of debate on

this question of relativity. TheEstablishment scientist wants tobelieve in relativity and no oneseems to question results whichsupport relativity. All the venomis directed at those who seek thetruth and need convincing.

In conclusion, it is relevant tomention that the so-called timedilation formula has only beentested for atoms and particles

moving at very high speeds,speeds far in excess of any ex-pected motion relative to thepreferred frame. The privilegedrole of the relativistic observerhas not been tested in this con-text.H. AspdenDepartment of ElectricalEngineeringUniversity of Southampton

'Vessot and Levine. Gen. Rel. and Gray..

vol 10 1979 p.1s1

Sibilantdistortion

Your issue of March has justarrived here. In it John de Rivazsays (Circuit ideas) that sibilantsare made unpleasant due to over -modulation . That they are oftenunpleasant or exaggerated is

true. but since Wrotham f.m.opened in 1951. I have been ledto believe that this is due to animbalance in the frequency re-sponse of the total overall audiosystem being used. Judicial useof audio equalizers (and not tonecontrols) seems to take care ofmost cases.

Your Dolby -inspired article ondigital audio equipment forbroadcasting in the same issue.with its variable but closely con-trolled variable pre -emphasis.ought to provide the tools tocheck this problem which soworries purists.

By the way, the BBC WorldService broadcasts. althougha.m. with limited audio top end.seem to have their audio soprocessed that voices soundnatural and without undueemphasis of the sibilants. Maybea BBC spokesman would care toexplain how they do this.Peter HirschmannHaifaIsrael

UntOrtunately the BBC's re-sponse did not arrive in time forincloino in this issue.


jp1 E._ OF'

QUOTATIONAttn J. SmithHYBRID ELECTRONICS LIMITED

Reference: 3449Your Ref: RD 2327

VA Rating: 500VARegulation: Approx 4%E/S Screen: No

Lead Type: SolidLead Length: Standard 20cm

Primary Windings: 0-220 - 240V (a 50HzSecondary Windings: 25- 0 - 25V (a 10A RMSOther Requirements: Built to the general requirements of IEC 742

Class 2, IPOOApprox Weight: 4.2Kg Approx Dimensions: 140 r 60mmMounting Method: 1 Steel + 2 Neoprene washers + Nut Bolt

Prices: Prototype cost for first transformer: £41.80 Then:10 - 24 - £25.43

25 - 99 £16.71100 - £14.81

Quoted prices exclude V.A.T. and delivery charges.We reserve the right to amend prices in accordance with currentmarket conditions.Minimum production batch = 10 pieces.Minimum call off - 25 off to qualify for discount price.Despatch: Prototype Order: 7-10 days

(21 days for non standard core)Quantity Orders: Please phone for currentlead timeGold Service: 7 working days(standard cores only)

STEEL DISHEDWASHER

OUTERINSULATION

7

CORE

END CAPS

Within the last 10 years ILP Electronics has become the largestmanufacturer of toroidal power transformers in the UK.Opposite we are displaying a typical quotation for a custom designtransformer, in the months to come other examples will be shown. Ifyou wish us to quote for an existing transformer or perhaps one forthe future, our CAD assisted design team will be pleased to quote.We have a large standard range from 15VA-625VA with primaries of120/240V which are available ex -stock (up to quantities of 25) from ourdistributor Jaytee Electronic Services, 143 Reculver Road, Beltinge,Herne Bay, Kent CT6 6PL - Telephone: (0227) 375254 - Telex: 295141TXLINK G Quote MBX 022735254.All standard transformers are supplied with a full mounting kitcomprising of 1 metal washer, 2 neoprene washers and nut, bolt +washer. On custom designs a variety of mounting methods areavailable including centre potting, threaded inserts etc.Our design department offers a speedy quotation and prototypedesign service with full engineering support including field calls ifrequired. Our manufacturing range is from 5VA to 5kVA with multipleprimaries and/or secondaries, to U.K. and International standards.Price stability:Our current policy is that prices are fixed for one year commencing1st January 1987.We also have expertise in designing for low acoustic noise, low strayfields and low temperature rise etc.

ILP ELECTRONICS LIMITED,Cotton Road, Wincheap Industrial Estate, Canterbury,Kent CT1 3RBTelephone: (0227) 454778 - Fax: (0227) 450507Telex: 965780 ILPAMP.

NEOPRENEWASHERSSECONDARY

WINDING

INSULATION

PRIMARYWINDING


/

.4(

0+-113 )

CONTROL SYSTEM DESIGNAND SIGNAL ANALYSIS FOR

THE BBC COMPUTER CODAS -PLUS: An enhanced version of the successful CODAS package for

control system design and simulation. Transient response, frequencyresponse and root -locus. Features include transport delays, non-linearities,compensators etc. Inclusive price f220.

SIGMA: A flexible package for signal generation, manipulation and analysis. Unique high-level language, forward and inverse Fast Fourier Transforms, time andfrequency domain convolution, multiplication etc. Features include flexible generation of signals and spectra, noise, non-linearities, quantisation. Inclusive price f190.

All packages have been designed for rapid interaction and flexibility and are suitable for use professionally and in teaching. Comprehensive manual and tutorial sessionincluded Details of these and other packages available on request.

Golten &Verwer Partners33 Moseley Road, Cheadle Hulme, Cheshire SK8 5HJ.

As described and illustrated in E& WW, June 87, page 647Telephone: 061-485 5435

ENTER i14 ON tEPLY CARD

STEREO MICROPHONE AMPLIFIER

STEREO MICROPHONE AMPLIFIER

V.PT, r0111

stil..n

161111 GRAN" lomt aolcuhoon

'JO or 2UU Odin ticriencer.,microphones to balancedlines

Variety of low frequencycharacteristics for improvingthe clarity of recordings

Inputs filtered against radiointerference

Complete boxed unit ordouble mumetal screenedamplifier module alone. Suitsdirect connection to digitalline inputs

Surrey Electronics Ltd., The Forge. Lucks Green, Cranleigh,Surrey GU6 7BG England. Tel: 0483 275997

A PAL PROGRAMMER CARD FORIBM AND AMSTRAD COMPUTERS

1116.it

IMPThis IBM PC/XT/AT andAMSTRAD compatible boardwill program a large range of20 and 24 pin PALs.Menu driven programmingsoftware is provided, alongwith a detailed manual.A fact sheet is availableon request.

Price: £395.00 + VAT

Available from: Guyvale Ltd. 0462 711434Address. 79 Bury Road, Shillington, Hitchin, HERTS SG5 3NZ

Telex: 265871 MONREF G (Quoting ref: KEY105 in the first line).


iS YouR boicliPMCNT&gal AQTTIN61

OIATX bATC a1ITS BASL)

CN AN IBM PCIKVAT ANDWILL Ac._<N113LE ANDDISASStvii.LE ANYFl2CCESSOQ Al2GUND IMp4Y,

PWS g.MuLATQ uP TOFCUQ 2-78C21;...1 PC2aasel51./P TO 27512. ATI5Ons

0515 717148

4mClathiki BARRERFREEFOSr FUTWICKBEDFORD MK* IYP ENALANDIt Ill (IN 1{1.:14.1(

OSCILLOSCOPES

CROTECH SINGLE TRACE 20MHz 3031/36 [199:2202mV-10Vidiv 40ns-0.2sidiv. Cal 0.2V. Component test3031: CRT 1 5kV 5x7cm. 3036: CRT 1 8kV 8x10cm

CROTECH DUAL TRACE 20MHz (@2mV) 3132 E2852mV 10V cm. ChltCh2. X -Y mode. Cal 0.2V1kHz sq 40ns-0.2sicm. Auto, normal or TV trig.Component comparator DC outputs Z input. CRT 2kV8x10cm

HAMEG DUAL TRACE 20MHz Itti2mV) HM203-6 (3142mV 20V crn Ch2t Chi X Y Cal 0 2V 2V 1kHz sq20ns-0.2s,cm Auto. normal or TV trig. Component testCRT 2kV 8x10cm

HAMEG DUAL TRACE 20MHz I@5mV1 HM204-2 E4181mV- 50V cm. Ch2- Chl. Sig delay. X Y modeY out. lOns- 1. 25s cm. Sweep delay 100ns- ls.Cal 0.2V 2V 1kHz. 1MHz. Z input. Comp. test. CRT 2kV8x10cm.

HAMEG DUAL TRACE 60MHz I@5mV1 HM605 E5831mV 50V/cm Ch2t Chl Sig delay X Y mode. Y out5ns-2 5s/cm. Sweep delay 100ns is Cal 0 2V.2V1kHz 1MHz Z input, Comp test. CRT 14kV 8x10cm

LEVELLfor INSTRUMENTS

HAMEG DIGITAL STORAGE 20MHz HM205 (4982mV 20V cm. Chi:- Ch2 Single shot and XY modes.2Ons 0 2s cm Auto, normal or TV trig Component test.Cal 0 2V 2V I kHz 1MHz Z input. Two 1K memories.100kHz samping Y out CRT 2kV 8x10cm

HAMEG DIGITAL STORAGE 20MHz HM208 E1460lmV-50V/cm. Ch2tChl Single shot and X -Y modes20ns-0 25s cm 20MHz sampling Two 2K memoriesPlotter output '3 IV cm, I0s/cm CRT 14kV 8x10cm

HITACHI DUAL 20MHz V212/2221223 £320/395/4751mV 12V/cm 20MHz at SmV. Chl ±Ch2. X -Y. Chl

output. 100n5-0 5s/cm Auto, normal or TV triggerCal 0.5V 1kHz square Z input CRT 2kV 8x10cmV222: Plus DC offset and alternate magnify function.V223: As V222 plus sweep delay lys 100ms

HITACHI DUAL 40MHz 1115mV) V422/23 1580/650As V2221/223 but 40MHz, 20ns/cm and 12kV on CRT

HITACHI QUAD 100MHz Itit5mVI V1050F f 1095Chl/Ch2 0 5mV 12V/cm Tugger Ch3/Ch4: 0 2V'cmDual time bases 2ns-0.5s/cm and 2ns-50ms/cm Signaland sweep delay CRT 20kV 8x10cm

THURLBY 8 CHANNEL MULTIPLEXER 0M358 1179Increases any oscilloscope to 8 channels Choice of tnggerfrom any channel. Response DC 35MHz

LOGIC ANALYSERS

THURLBY LOGIC ANALYSERS LA160A/B 1395/49516 data charnels. Clock DC 10MHz 120MHz for 81 Binary,octal, decimal, or hex formats.

COUNTERS & OSCILLATORS

COUNTERS MET100/600/1000/1500 199/126/175/1998 digit 0.5" LED. 5Hz up to 100/600/1000/1500MHz.Resolves 0.1Hz. Sensitivity 5rnV up to 10MHz. Low passfilter. Mains/rechargeable battery powered.

LEVELL RC OSCILLATORS TG152D/DM [99/1253Hz-300kHz. 5 ranges, acc 2% + 0.1Hz up to 100kHz,3% at 300kHz. Sine or square <20(4N to 2.5Vrrris. Distn<0 2% 50Hz 50kHz. TG152DM has an output meter

LEVELL RC OSCILLATORS TG200D/DMP 1139/1751Hz 1MHz 12 ranges, acc 1 5% + 0 01Hz to 100kHz 2%at 1MHz. Sine or square outputs <200IN 7Vrms.Distortion <0.05% 50Hz-15kHz. Sync output >1VTG2000MP has output meter and fine frequency control

LEVELL DECADE OSCILLATOR TG66A 13300 2Hz 1.22MHz. 5 ranges. 4 digits, acc 0.3%6Hz 100kHz. Sine output <30yV-5Vrms 2dB/ + 4dB andV scales. Distn <0.15% 15Hz-150kHz Mains/battery

LEVELL FUNCTION GENERATORS TG302/3 1136/2360 02Hz 2MHz in 7 ranges Sine, square, tnangle, pulse andramo 20mV to 20Vpp from 5052 DC offset 0'10y TTLoutput. TG303 also has a CMOS output and 6 digit 10MHzcounter with INT/EXT switch.

OTHER INSTRUMENTS AVAILABLE - FREE DELIVERY MAINLAND UK -QUANTITY DISCOUNTS -VAT EXTRA

LEVELL ELECTRONICS LTD. Moxon Street, Barnet, 'Herts., ENS SSD, EnglandTelephone: 01-440 8686 & 01-449 5028

ENTER TON REPLY (..-11{1)


Europe's capacitormarket

Whilst the semi-conductor industryworries itself about the

cost of R&D and strategic mer-gers to breech the $1bn billings'critical mass,' the capacitor in-dustry worldwide is facingsimilar issues of profitability andtechnological and businesschange. Over the last two or soyears, many household names in

For many years the somewhat slow moving andmature capacitor industry has been overlooked byinvestment interest and PR pizzaz. But there are

changes afoot, in both market and industry.

KEITH THOMAS

40

30

20

10

0

ir- Py ri

4

--

1082 19e3

tantrum

W. CAM -

'484 1Per

r`4r4140 r- Fo.,.

F g.l. Percentage share of the total capacitor market enjoyed bythe major dielectric families from 1982 to 1986.

capacitors have declared the desire for amerger with a stronger group. Some haveopenly declared unprofitability followed by

rapid posting of 'For Sale' notices. Only inFrance is there evidence of bullish invest-ment being made to increase manufacturing

capacity of technologies thathave much less than averagegrowth. Elsewhere, it is ex-clusively the ceramics housesthat have been spending money.

The shake up of the industryhas followed a radical shift in thetechnology used by circuit de-signers, as shown in Fig.1. Fromthis illustration it is evident thatthe dielectric flavour of the

month is ceramic - and multilayer ceramicat that. The tantalum, aluminium and filmindustries have lost market share to cera-

Fig.2. Change in packaging of the tantalum capacitor elements Fig.3. During the last three years consumer preference betweennote the rise in popularity of the chip packaging style. paper and film capacitors has been almost static.

Fig.4. Emerging popularity of the chip packaging style in the Fig.5. Since 1984 the package styles of aluminium capacitors haveceramic dielectric is largely at the expense of discs. moved slightly away from the large cans and axials to small cans.


Fig.6. Smoothed forecast of the likelygrowth of capacitors in Europe to the endof the decade.

mic, which has trebled its share of theEuropean market since 1982. Comparisonwith the US market will show an evenstronger move towards ceramic, since theUS does not have the installed and some-what protected film dielectric manufactur-ing base that is characteristic of Europe.

Figures 2 to 5 show the movements withineach dielectric of the packaging of thedielectric. It should come as no surprise thatthe chip package is becoming popular at theexpense of the traditional parts. The trend tosurface mounting is of course playing havocwith the relative market shares of eachdielectric, since the ceramic capacitor isideally suited to the surface mount assemblyprocess - manufacture of a leaded part startswith a stand-alone chip. The other technolo-gies must add extra manufacturing processsteps to their capacitor element to protect itfrom the harsh soldering environment,shrugged off by the ceramic dielectric,thereby increasing cost. The most at riskfrom the move to SMT is the small alumi-nium and film dielectrics that shy from thesoldering processes used.

Interestingly, the tantalum capacitor isforecast to fare well in this trend to SMTsince no other dielectric can offer thevolumetric efficiency at the cost, so the roleof 'replenisher' or topper up of on -boardcapacitors will remain the domain of tanta-lum, whether leaded or chip. However, themove to SMD in all dielectrics is mostpronounced in ceramic, in particular forconsumer applications.

FOR THE FUTURE

The capacitor market is forecast to keep ongrowing. The relentless pace of the electro-nics industry is utilising electronics technol-ogy for more applications in all sec-tors. The computers, consumer, com-munications, instrumentation and controlindustries have depended absolutely uponutilisation of electronics, and now newcom-ers, the car industry, are starting to exhibitstrong demand as they embrace electronicstechnology. The defence industry hit, withcutbacks worldwide, are utilising theirsomewhat reduced disbursement in a differ-ent manner. Gone are the projects for biggerguns - they are replaced with more sophisti-cated projects that improve control ofweapons, and improve communications andintelligence, which all need electronics. Sodefence budgets are favouring a very strong

20G

150

100

60

0

Indek-qi bookiricri

11111111111111111111111111111984 1986 1988 1987 1988 1989 1990

60%

50%

40%

30%

20%

10%

0%1887

Tantalum

Oth-r

1888

Aluminium

1888 1990

Chramlc M/L P 8 Film

Fig.7. Expected movement of designer prefere-ice for each dielectric as the marketgrows in the coming years. Notice the enormous growth forecast for ceramics.

swing to more electronic equipment. Thecommunications industry too is lifting offwith strong demand for mobile communica-tions: cellular radio is the driving force.

The capacitor element of this growth isforecast to grow about 9-10% in 1987 and alittle more in 1988 - 12-14%. Beyond thatpundits are already speaking of the nextslowing down of demand that hits the elec-tronics industry from time to time as supply.stocks and demand move out of line. Duringthat time, SMD is forecast to grow rapidly byas much as 50% a year and it is clear that thewinners are going to be ceramic and tanta-lum dielectrics. The others will find theirniche which will keep some of the machinesrolling- in many applications the traditionalthrough hole technology remains the opti-mum choke - but it is clear that there are agalaxy of companies, large and small, thatplan to move into surface mount in thecoming year.

In terms of numbers of units, the general -use on -board capacitors dominate total de-mand. They are the most affected by thechange in assembly technology and so mas-sively influence the global numbers. Foroff -board capacitors, the large power correc-tion capacitors, or the large aluminiumcans, the growth pattern is individualistic

and it is misleading to offer a global growthfigure since these capacitors tend to beend -use, application -specific. However, it isclear that in medium power applications,incumbent energy storage capacitors will beeventually replaced with smaller devicesworking at high frequency. The dielectricchosen for this application is most likely tobe ceramic in the medium to long termalthough aluminium will continue to findfavour in the short term. This is because theESR of ceramic at 1MHz is much lower thanaluminium or wet tantalum, and at thesefrequencies the consequential capacitancerequired falls dramatically to a few microfar-ads. Savings can be made not only in termsof microfarads, but also in the size and costof the magnetics which at 1MHz are afraction of those at 50Hz or 40kHz.

We may then refer to Fig 6 & 7 to forecastthe likely future for capacitor demand bydielectric and numbers of units sold. It lookssound for ceramic and not too bad fortantalum, but we trust the manufacturers ofother dielectrics have already selected theirniches.

Keith Thomas is vice-president of sales andmarketing, Europe, forAVX ofNew York.


Capacitor technologiescompared

Ceramic, plastics film, or electrolytic? With significant overlaps incapacitance value, it is important that design engineers have a good

appreciation of the factors involved - especially in todays cost -sensitive markets.

Every year, as capacitor technologiesimprove and are stretched to newlimits, the complexities and the eco-

nomics of the enormous variety of styles,materials and performance characteristicsbecome more difficult to understand.

Miniaturization, new materials and newproduction techniques have resulted insome radical, and many subtle changes inthe range of capacitors available today.

The majority of capacitors used in electro-nic engineering fall within the spectrum ofone picofarad ( 1 pF) to 220,000 microfarad(0.22F) and are grouped into a number ofmain technologies. They include ceramic -based capacitors, film or plastics types andaluminium/solid aluminium/tantalum capa-citors.

Each of these technologies cover typicalcapacitance values as shown in Fig. 1.

Perhaps the most complex area is theoverlap of ceramic and film technologies forwhich the following comparisons andobservations can be made.

FILM CAPACITORS

Plastics -film capacitors utilise one of fourmain plastics films for their dielectric mat-erial; each has advantages and disadvantageson performance, stability, dielectricstrength. environmental resistance andcost.

The film dielectric is either stacked, ormore commonly wound with electrodelayers to form a capacitor cell. The electrodelayers may be metal foil or the cell may be anintegral winding of metallized film (theelectrode layer being vacuum deposited ontothe film). This metallized film constructionrealises a very size and cost efficient capaci-tor: it does, however, have a limited pulseload capability (see Table 1). A film/foilconstruction by comparison has significant-ly better power handling (pulse load) capa-city but will be larger and more expensive.

Four main plastics films are used asdielectric material: polyester (PETP) poly -carbonate, polystyrene and polypropylene.Each has its own unique features.

Polyester is by far the most commonlyused material due to its low cost andreasonable performance characteristics.Moderate voltage ratings, pulse load charac-teristics, temperature and frequency stabil-ity all combine to produce the ideal purposecapacitor. The cell is almost always of metal -

MARTIN BAKER

Capacitance spectrum per major technology

01

Wet electrolytic /Solid a.maum/ tantalum

Fig.1. The most cost-effective technology will vary depending on basic capacitance valueand on a multitude of other interactive parameters.

lized film construction and frequently in a5mm lead pitch module for which capaci-tance values up to 1µF can be producedreliably and economically.

Polycarbonate is a higher performancealternative to polyester for general purposeapplications. Capacitors in this materialcommand a price premium (typically +15 to+30%) and offer improved stability ofcapacitance (AC) with changes in tempera-ture and frequency. Maximum voltage rat-ings and pulse load characteristics are alsobetter than those of polyester. The use ofpolycarbonate capacitors in modern circuit-

ry is declining and hence this dielectric isonly offered by a few major manufacturersleg Philips).

Polystyrene is probably the most com-monly used material for precision 1% toler-ance capacitors. Usually in a film/foil con-struction, polystyrene provides optimumstability of capacitance with temperaturechange. The capacitance/temperature rela-tionship is linear with a -125ppm tempera-

Fig.2. Sintered ceramic electrode multi -

layer construction creates a size -efficientand reliable capacitor.

Table 1. Typical pulse load limits in V/p.s for metallized film capacitors (based on pulse voltages equalto the rated dc voltage)

Rated d cvoltage

Lead pitchdielectric.

5mmMIST

7.5mm lOmm 15mm 22.5mm 27.5mmMkT MkT MkC MkT MkC MkT MkC MkT MkC

63 55 17 15 6 - 3 - 2100 90 30 24 30 10 13 4 6 3.5 4.5250 60 35 45 14 18 6 8 5 7400 95 55 70 22 30 10 13 8 1

MkT: metallized polyester. MkC: metallized polycarbonate.


ture coefficient (t.c.) ie - 0.0125% reductionin capacitance per degree of temperatureincrease above 22°C. with capacitance valuescovering typically 10pF to 100,000 pF at±1% tolerance and with the stable andlinear-t.c. polystyrene capacitors are mostfrequently used in applications requiringtemperature compensation, also tuned cir-cuits and filter networks.

Polystyrene is however relatively expen-sive and is significantly limited by its maxi-mum operating temperature of around85°C. As a result polypropylene film/foil isbecoming increasingly important for preci-sion film capacitors. While still offering±1% tolerance on capacitance, a relativelystable t.c. (-125 to -250 ppm), and capaci-tance values approaching 0.1 µF; polypropy-lene meets -40/+100°C environmental re-quirements and is less prone to thermalshock during soldering.

Polypropylene also performs well withhigh voltage and is consequently used inhigh pulse/small power capacitors. Metal-lised or double metallized polypropylenewound with foil can achieve voltage ratingsin excess of 2000V dc and is often an idealchoice for a.c. applications, Polypropylenecapacitors have traditionally been used indeflection circuitry and as flyback capacitorsin tv applications and are now being com-monly used in switch -mode power supplies.

Table 2 summarises some of the charac-teristics of the principle film dielectrics.

CERAMIC CAPACITORS

Two construction methods are used for themanufacture of ceramic capacitors.

Single -layer types consist of a single rec-tangular or discoidal layer of ceramic mate-rial with a silver or (for higher reliability)copper electrode on each side of the ceramic.Leads are soldered to the electrode layersand the capacitor is protected by a mouldedbody or cost effective lacquered coating.

With multilayer devices very thin (20-25p.m) layers of ceramic interleaved with offsetprecious metal electrode layers are pressedand then sintered at high temperature toform a very compact and volumetricallyefficient monolithic capacitor 'buildingblock'. Leads are soldered to this block orsurface -mounted -type terminations are ap-plied (Fig 2).

Ceramic capacitors are spilt into two main

Table 2. Main plastics film dielectrics -typical parameters.

Capacitancerange

(pF.nF.I.LF)

Tolerance Max.dc

voltage

Temperaturecharacteristic

Pulse loadlimit'V/ps

Temperaturerange

'CRelative

cost

Polyester 1000pF-101.1.F ± 10% 630 Non-linear Typically -55/+100 Low(MkT) ± 20% ." C - 3%

to 4- 7%25 - 50

Polycarbonate 1000pF-100 ± 5% 1000 Non linear Typically -55/+100'(MkC) ± 10% AC < ±2% 30-70

Polypropylene 47pF-62nF ±1% 1000 -125 to High -40/ + 100°(precision) -250ppm

KPPolypropylene

(power)1000pF-1µF ± 5% >2000 -125

to -250ppmVery higheg 2000

-55/ +85

(Kp/mmkp)Polystyrene 10pF-02211F ± 1% 630 - 125pm High -40/+85" High

(kS) ±2.5%

Pulse load limits based on 10mm pitch capacitor for MkT MkC across 100-400V dc rated devices.

.20

.10

at -j o

tt -10t(z -20

Ls, -30

-40

X7R Dielectr,c

NPO Delectni

Z5U Dielectn(

-55 -35 -15 .5 25 45 .65TEMPERATURE (n)

MI5 425+125

-64)-

4PC013G I

X7R

-80'

0 5 10 15 20 25 30 35 40 45

APPLIED VOLTS Id c

so

tk 10k 100k 1M 10M

FREQUENCY I Hz)tIVARIPV

Fig.3. NPO dielectric outperform X7R. Z5Uand Y5V but has a limited capacitancerange and is expensive when measuringcost per picrofarad.

classes depending on the type of ceramicmaterial used.

Class I types utilise low K materials whichresult in low losses and stable linear temper-ature dependance.

Class II types have higher losses andnon-linear temperature characteristics; theyare often subdivided into medium K and highK materials.

The three most common 'industry classi-fications' for ceramics are NPO (or COG),X7R and Y5V/Z5U. Cost per microfarad andthe performance characteristics of thesematerials are proportional

Table 3: The relative cost a performance of a filmcapacitor varies depending on which dielectricmaterial is incorporated.

Type Cost Performance(stability of capacitance with

changes in temperature.frequency and voltage)

NPO (COG) Most Bestexpensive

X7R

Y5V/ZSU Leastexpensive

Worst

NPO devices, and capacitors with a similart.c. (always linear and usually between zero(NPO) and -750 ppm (N7501). fall into theclass I category. Capacitance values rangefrom 1 pF to around 1,000 pF for single layerdevices and up to 10,000 pF for multilayertypes, are typically specified with ± 2% or ±5% tolerance. Class II devices show little orno capacitance change with increases infrequency or voltage and are therefore usedin 'precision' applications in tuning andtiming circuitry.

Class II devices include X7R (medium KIand Y5V/Z5U (high K) types. Both shownon-linear relationships between capaci-tance change with temperature, voltage andfrequency increase, see graphs 1-3. They aresubsequently used in general purpose ap-plications Y5V/Z5U material is most com-monly used for decoupling capacitors whileX7R is frequently interchangeable withpolyester film.

CAPACITOR ECONOMICS

A simple cost comparison of the manydifferent types of capacitor is impossible. Inthe precision area, polystyrene, polypropy-lene and class I ceramic, it is clear that thelatter is most cost-effective for low values upto 1000pF. Between 1000pF and 4700pFprices of ceramic and film are similar whilefor higher capacitance values film capacitorsbecome more cost effective.

In the general purpose area, ceramicsagain are the most economic choice forlower capacitance values (100pF to lOnF).Between lOnF (0.01g) and 0.470 ceramicand film prices are comparable. For highervalues metallized polyester then becomescost effective with metallized polycarbonateproviding a higher performance but moreexpensive alternative.


Terminations forsurface -mounted multi -

layer chip capacitorsThe choice for terminations for ceramic chip capacitoris between the lower cost of the nickel barrier and the

greater reliability of silver -palladium type

The spread of surface -mount techno-logy beyond the realms of the thick -film hybrid has promoted component

manufacturers to re -assess the materials andtechniques involved in the design and con-struction of surface mounted components.Much of this research is being concentratedon the metallized terminations of ceramicmultilayer chip capacitors.

Unlike leaded, through -hole components,where the mechanical strength of the sol-dered joint is reinforced by the componentlead, the s.m.d. must rely on the quality ofthe soldered joint alone for both electricaland mechanical integrity.

The advent of high-speed placementmachines and improved mass -solderingmethods mean that zero -defect soldering isthe ultimate goal of the equipment manufac-turer who is to capitalise on the cost-effectiveness of surface -mount technology.It is essential that both the solderahility andreliability of the component end -

terminations are at the highest possible levelprior to assembly.

This article discusses the advantages anddisadvantages of the two methods currentlyused in the manufacture of multilayer cera-mic capacitor terminations. Comparisonsare made between silver -palladium termina-tions and those using a nickel harrier be-tween the internal electrode structure andthe outer solderahle layer of termination.Each type is evaluated for wettability duringsoldering. ability to withstand thetemperatures and dwell -times involved inboth wave and reflow soldering, resistance todemetallization at soldering temperatures.ability to maintain a solderable surfaceduring handling and storage under varyingconditions, and cost-effectiveness.

Prior to end -metallization. prefabricatedceramic capacitors are cut to length. fired.and subjected to a tumbling process underprecisely determined conditions. This tumb-ling action rounds off the edges and cornersof the ceramic to enable a subsequent layerof either silver/palladium alloy or pure silverand nickel to he applied evenly over thesurfaces. necessary to help prevent dissollu-tion of the termination by molten solder.

TERMINOLOGY

Wettability - Ability of the metal termina-tion to be wetted with molten solder withina specified time without subsequent de -wetting. It depends on the materials usedfor the termination and the level of con-tamination of the surfaces brought aboutby ageing. storage and handling.

Soldering temperatures - The solderingtemperature will depend on the meltingpoint of the solder used in the process,usually between 215 and 235 C for themajority of solders used in the manufac-ture of electrical circuits, but in somecases as high as 260 C.

Dwell time - The time taken for the compo-nent to reach the soldering temperatureand for the solder to flow in the joint areadepends on the thermal demand of thecomponent, which depends on the size.construction, and the materials used.Dwell time varies according to the solder-ing method used, typically five seconds forwave soldering, eight seconds for reflow.and up to 30 seconds for vapour -phasereflow.

Resistance to demetallization - Ability ofthe termination to withstand solderingtemperatures without dissolving. Demetal-lization usually increases with extendeddwell times.

Maintenance of solderability - Wettabilityof the termination surfaces is affected byageing storage, transit, and handling. Mate-rials used for the terminations and themanufacturing process can also effectageing. and hence solderability.

SILVER -PALLADIUM TERMINATION

The composition of the silver -palladiumalloy is very important and research hasshown that the correct percentage of palla-dium is vital for the control of both demetall-ization and silver migration. Demetalliza-Lion can cause a build-up of silver con-tamination in the solder bath, giving rise tothe formation of solder bridges on the

finished substrate. This can entail expensiveand time consuming re -work. The migrationof silver across the surface of the capacitor isan on -going problem during its whole life-time. and can cause the degredation, break-down, and ultimate failure of the capacitorin the field. Mullard ceramic chip capacitorterminations contain 35% palladium, morethan in any other brand, which experimentshave shown to be sufficient to prevent silvermigration under all but the most severeconditions (see Table).

Termination Time for Time tocontent first signs of short-circuit

Pd Ag migration (min)(min)

0 1.00 0.5 2.00.11 0.89 0.5 4.50.22 0.78 2.0 8.00.33 0.67 15.00.35 0.65

The silver/palladium alloy, in the form of apaste to which powdered glass is added. ismanufactured 'in-house' under controlledconditions to ensure optimum compositionand rheological properties, and quality con-trol tests are carried out on each batch ofpaste. The paste is applied to the ends of thecapacitor, usually by a controlled dippingmethod, to provide a uniform layer. Thislayer is approximately 35 µm thick on thetop and bottom faces, and 100 p.m on the endface after the capacitor has been fired asecond time to form the alloy.

Wettability of silver and silver alloys is high,arid well -proven in the electronics industry.and under normal conditions of storage andhandling, less prone to oxidation than tin:lead.

Resistance to demetallisation. Class is in-cluded in the alloy to improve adhesion ofthe metallization to the end faces, and also toreduce the rate of dissolution of the termina-tion by molten solder. Exhaustive tests haveshown that Mullard ceramic multilayer chip


capacitors with silver -palladium termina-tions can withstand the temperatures anddwell times encountered during either wave.reflow or vapour phase soldering withoutany significant demetallization of the ter-minations. However, a small amount ofsilver dissolved into the solder joint beneaththe component is advantageous when thefinished substrate is likely to be subjected tothermal cycling: it renders the joint morecompliant and enables it to compensate forthermal mismatch between the componentand the substrate.

Maintenance of solderability. Regular quali-ty checks, including accelerated ageing teststo determine the effects of air pollution(HS). oxidation in air, and corrosion on thesilver -palladium terminations show thatunder normal storage conditions a high levelof solderability is maintained for up to twoyears. However, under harsh conditionswith a high level of air pollution, storage in acontrolled environment is recommended.

NICKEL BARRIER TERMINATIONS

The manufacturing process for the body of acapacitor is the same as that for the silver -palladium type, but after tumblingto round off the corners and edges.the end connections are first formedby applying a controlled amount ofpure silver paste. This provides auniform termination approximately35 pm thick on the top and bottomfaces and 100 Ian on the end facesafter the second firing.

Because silver dissolves rapidlyinto molten solder, a 2 to 3µm layerof nickel is plated onto the silver toprevent dissolution. Unfortunately.nickel is difficult to solder at thecomparatively low temperaturesand low flux activity necessary in themanufacture of electronic circuits.To overcome this, a further 10 to 12p.m layer of either tin or tin/lead isplated onto the nickel to improve itssolderability.

Unlike silver -palladium termina-tions, where the composition of thetermination and that of the capaci-tor electrodes are similar. the nickelbarrier types may be subject to'material transport' whereby puresilver from the base terminationmay diffuse into the silver -palladium of the electrodes. Howev-er, this can be overcome by carefulcontrol of the process parametersduring the second firing.

Unless particular care is taken dur ng theplating processes, conditions may arise thatcould lead to defects during assembly or inthe field: If the chips adhere to one anotherin the plating container, or are not evenlydistributed. the plated layer may not be ofuniform thickness of may even be missingaltogether. If the nickel layer is missing orintermittent, the underlying silver will bedissolved rapidly into the molten solder, sodestroying the termination. A missing orintermittant layer of tin -lead, exposing the

nickel barrier will adversely affect the solder-ability of the termination.

In practice, a layer of tin, to which a verysmall amount of lead may be added to inhibitthe growth of tin 'whiskers', is preferred toeutectic tin -lead. This is because particles ofthe comparatively soft tin -lead may be pro-duced by abrasion during handling, whichunder humid conditions, can cause trackingbetween terminations or between conduc-tors on the substrate.

During firing, microcracks may developin the ceramic body of the capacitor. Ioniccontaminants, inherent in the plating pro-cess, may become trapped in these micro -tracks. These contaminants are very difficultto detect and remove, and because theydissociate into free ions which are goodconductors in humid conditions, may causecircuit failures in the field. They are also

Fig.1. The silver/palladium terminations ofceramic multilayer chip capacitors con-tain 35% palladium and are approximately35 µm thick on the top and bottom faces,and 100p.m on the end faces. The roundedcorners help prevent dissolution duringsoldering.

Resistance to demetallization. The nickelplating is an effective barrier to dissolutionand affords total protection against demetal-lization under even the most aggressivesoldering conditions.

Maintenance of solderability. A solder sur-face of pure tin remains solderable for aconsiderable time. However. there is a

theory that the use of pure tin could give riseto the growth of tin whiskers. causingreliability problems. The addition of a smallamount of lead to the tin. however, inhibitstheir growth. A tin -lead layer has goodsoldering properties when newly made but issusceptible to oxidation in humid condi-tions. so protection from the atmosphere isdesirable.

OVERVIEW

The important factors to be considered whenchoosing between nickel barrier or silver/palladium terminations are resistance todemetallization, solderability. the reliabilityof both the component and the solderedjoint, and the cost. With normal solderingtemperatures and dwelling times, the resist-ance to demetallization of silver -palladium

is high, and well within acceptablelimits, providing the palladium -to -silver ratio is correct (35Pd:65Ag1and the layer is of uniform thick-ness. This resistance decreasesrapidly as soldering temperaturesand dwell -times rise above normallevels, especially at the cornerswhere the layer may be thinner.

Nickel barrier terminations onthe other hand remain highly resis-tant even under the most aggressiveconditions, providing the manufac-turer employs a high level of qualitycontrol to ensure that the plating isuniformly deposited.

The solderability of both typesremains high under normal storageconditions, whilst in a more aggres-sive environment the solderabilityof silver -palladium or pure tin is

probably better than that of tin -lead.The extra plating processes requiredby the nickel barrier terminations.and the possibility of ionic con-tamination. can cause reliabilityproblems in the finished product.On the other hand, the smallamount of silver that dissolves intothe joint with silver -palladium tendsto strengthen the joint and so im-prove reliability. The present-daycosts of noble metals. especially

palladium, makes the silver -palladium typesmarginally more expensive than the nickelbarrier, even though more processing isrequired for the nickel barrier. With normalmanufacturing processes and optmized stor-age and handling conditions, the decidingcriteria may well be the slightly lower cost ofthe nickel barrier type and the greaterreliability of the silver -palladium.

Fired ceramicdielec nc

Silver / Palladiumtermination

Silver/Palladiumtermination

Electrodes

Fired ceramicOuter solderable dielectric

layer

Silver basetermination

Intermediate layer of galvanic nickel

Electrodes

Fig.2. The 2 to 31im intermediate layer ofnickel prevents dissolution of the basetermination during soldering.

highly reactive with metals and producecorrosive ract ions.

Wettability. With effective plating, the wet-tahility of the tin or tin -lead surface is good.better perhaps than silver -palladium, butany thin or void areas, exposing the nickel.greatly reduces the wettability.

This report is drawn from information sub-mitted by Mullard Ltd.


SOAR'S DELUX ME4040 DMMWITH BAR GRAPH DISPLAY

UNMATCHED VERSATILITY AND PERFORMANCE

3 YEAR WARRANTYRELATIVE. FREQUENCY TEST. DATA HOLD FUNCTIONS

SOAR'S ME4040 DMM is part of the excitingBar Graph Display DMM's now availableincorporate the most advanced Japaneseavailable. New custom designed chipsproduced an advanced range of DMM'sexepcted on models which are twice the cost.

4000 series range offrom SOAR, whichtechnology currentlyand circuitry havewith features only

The 4000 Series is a comprehensive range of five models whichenables you to select the appropriate model for your ownapplication. All models come with a three year warranty and areavailable direct to yourselves at prices starting from as low as£69.00.SOAR'S complete range of T&M Equipment has an enviablereputation throughout the world for manufacturing high qualityproducts at extremely competitive prices. Extensive productplanning takes place throughout the year which leads toproducts with total uniformity of operation. The range ofequipment available is extensive, from a basic pocket DMM to themost sophisticated industrial energy monitor.

SOAR PRECISION TEST 8 MEASURING

EQUIPMENT AT EXTREMELY

COMPETITIVE PRICES

FEATURES ME4040: High speed autoranging. High speed sampling with the use of a 40 segment bar graph

display. Heavy duty rugged case and circuit, which is dust and grime

proof and is designed to withstand accidential dropping. Auto or manual ranging with continuity beeper and diode test. Auto power down mode. Relative, frequency and data hold functions. High accuracy: DC V 0.3% rdg. Extended capabilities with the use of plug in adaptors which

cover temperature, high AC/DC current, capacitance andtransistor hfe/loss measurements.

SOLEX HAS NOW BEEN APPOINTED THE EXCLUSIVE UK

REPRESENTATIVE FOR THE COMPLETE RANGE OF SOAR

TEST 8 MEASURING EQUIPMENT

For further details of SOAR'S ME4040 DMM. together with infor-mation on the complete range of SOAR T & M Equipment contact:

IEXINTERNATIONAL

44 MAIN STREET TEL: (0455) 283486BROUGHTON ASTLEY TELEX: 378353LEICESTER LE9 6RD FAX: (0533) 544248


Z80 CONTROL Z80CARDMASTER CPU

46 MHz Z80 CPU

CP M compatible User transparent MULTI -TASKING

Up to 32K EPROM 8 16K RAM

Watchdog crash protection

RS232 & RS422 Comms

2' Z80a PIO (one uncommitted)

On board bus buffering

1

a..

: -

....> -4r--

Power -on jump hardware Euro-card construction

NOW FROM £124 + VAT

CUB MICROCONTROLLER 2130 CPU

4 Z80a PIO's (6410 lines)

Z80a CTC 4K Battery backed RAM (2K sup.)

4K EPROM (2K MCV2.0 sup.)

Powerful monitor (MCV2.0)

Eurocard construction

4

100

°

--

-.= ,,

NOW FROM £108 VAT

STARBURST V1.31A CROSS ASSEMBLER FOR

CMR16 NOW FROM£199.00

CP/M80 covers four majorfamilies of single chip uP's and

uC's* 8048 inc. 8741/2 8748/9/50* 8051 inc. 8031/2 8751 8744* 6801 inc. 6800/1/2/368701* 6805 inc. 68705 63705

Bare PCB's Available1+ 10+

C/M CPU 28.50 25.65C/M I/O 28.50 25.65CUB 23.50 21.15CMR16 40.00 36.00

Supplied with a complete set ofdemonstration files.

STARBURST V1.31 £95.00+ VAT

Requires Z80 CPU

Manuals on request

GNC ELECTRONICSLittle Lodge, Hopton Road,

Thelnetham, DISS IP22 1JN.Tel: 0379 898313

ENTER 2s ON It PI, )(CARD

SMALL SELECTION ONLY LISTED - RING US FOR YOURREQUIREMENTS WHICH MAY BE IN STOCK

Racal Solid State Communication Recel-yews - RA1217 - Mechanical digit readout 1

304.4C/S C300 Racal RA17L Communi-cation Receivers 500KG/S to 30MC/S in 30bands 1MC/S Wide - £175 - All receivers are airtested and calibrated in our workshop -supplied with dust cover - operationinstructions - circuit in fair used conditionRacal Synthesisers (Decade frequencygenerators) MA250 - 1 6MG'S to 31 6 MG/S -£100 MA1350 for use with RA17 receiver -£100.MA259G - precision frequency standard5MC/S - 1MC S 100KHz - £100 to £150. RA137and RA37 - LF convenors 10 to 980KC/S - £40to £75 RA98 SSE-ISB convenor - £50. RA121SSB-ISB convertor - E75 Plessey PR155GSolid State recervers - 60KC/S - 30MC/S - £300.Trenstel Matrix Printers AF11R - 5 levelbaudol code -- up to 300 bauds - for pnnt out onplain teleprinter paper - £50 Army Field

Telephone sets type F L and J - large quani4,in stock - C6 to £15 depending on type altoquantity. P 0 R Don 10 Telephone Cablehalf mile canvas containers - £20 NightViewing Infra -red periscopes - twineyepiece - 24 volt DC supply - £100 EAOriginal cost to Government over E11.000 EAStatic Inverters - 12 or 24 volt input - 240 voltAC sinewave output - vanous wattages P 0 RXV Plotters and pen recorders - venous -P 0 R Signal Generators - various - P 0 RTF 893A - Power meter - £50 Racalfrequency counter type 836 - £50 Tektronicplug -Ins - 1A1 C50 1A2 £40 1A4 £100 M £50All items are bought direct troth H MGovernment being surplus equipment Price isex works S A E for enquines. Phone forappointment for demonstration of any items.also availability or price change V A T andcarriage extra

EXPORT TRADE AND QUANTITY DISCOUNTSJOHNS RADIO, WHITEHALL WORKS,

84 WHITEHALL ROAD EAST, BIRKENSHAW,BRADFORD BD11 2ER. TEL NO: (0274) 684007WANTED: REDUNDANT TEST EQUIPMENT - VALVES - PLUGS - SOCKETS,

SYNCHROS ETC. RECEIVING AND TRANSMITTING EQUIPMENT I

TRANSFORMERS EX -STOCKMAINS ISOLATORSPrig Sec 120V 2 OR

240 to 415440V160-1000VA Tap Secs)

VA C P&P'20 7.06 2 1860 11.51 231

100 13.43 2.59200 19.03 3 10250 23.01 3 24350 28.46 3 40SOO 35.45 3.66000 64.28 4.62500 82.92 5 85

2000 99.76 6361000 139.89 OA0000 298.89 OA

50Vs

2 AM

4 P6 S

81012

25V C P&P1 5.01 1 762 6.09 I 904 10.84 2206 12.54 2 258 17.16 258

12 21.81 2 7916 30.89 31520 36.66 3.6024 43.87 3.80

30.15V or 15.0-15V2. 15V Tap Secs. Volta30V 15V C P&P

3.86 1 411 2 5.24 1.702 4 8.47 1.923 6 9.82 2 104 A 8 11.72 2205 M 10 14.49 2.316 P 12 16.40 2 558 S 16 21.95 2.60

10 20 25.32 2.84121 24 28.07 2 95

20 31.66 3.5120 40 43.22 5 95

60v 30V C P&P0.5 1 5.69 1 85

1 2 8.67 1 912 4 11.15 2203 A 6 16.12 2.344 M 8 18.38 2.555 P 10 23.23 2.786 S 12 26.50 3.02

16 37.25 3.6510 20 43.37 39912 24 49.98 4 65

24/12V or 12-0-1282 r 12V Secs. Pd. 240V12V 24V C P&P

05 025 3.08 1.501 0.5 3.70 1.602 1 5.15 1 704 2 5.94 1906 A 3 9.31 2058 M 4 10.89 2 10

12 P 6 13.20 2.2516 S 8 15.73 2.6020 t0 21.17 30430 15 26.31 3.1040 20 37.56 3 7560 30 53.92 49083 41 62.09 5 65

INVERTERS12(24V DC to 240V ACWINDING SERVICES

3VA 10 15KVACONSTANT VOLTAGE

TRANSFORMERS & UPSfor Spike -free Stable

MainsALSO VALVE MAINS

OUTPUT A MATCHINGTYPES

PLEASE ADD 15% VAT TO ALL ITEMS AFTER PAP

BARRIE ELECTRONICS LTDTel: 01-555 0228 (3 lines)

AUTOS105,115.220.230,240VFor step-up or downVA C P&P80 5.86 1 70

150 8.49 1 85250 10.34 198500 16.12 268

1000 28.79 3.251500 34.17 3682000 51.09 4 623000 86.88 5 724000 112.78 OiA5000 131.33 OA7500 202.71 OA10KVA 239.53 OA

CASED AUTOS240V Cable Input

115V LISA socket outlet,VA P&P

20 8.34 1 7680 11.33 1 87

150 14.67 2 20250 17.87 3 02500 29.32 3 19

1000 40.29 4 342000 73.33 5 283000 105.26 OA

Full range AVO s.Meggers.

TOROIDALSWound to Order

Unit 211, Stratford Workshops,Burford Road, London E15 2SP

694



rCIRCUIT IDEASCurrent limited 0-200V supplyAn outline in the National Semiconductordata book provided the starting point for this0-200V power supply. Current limitingoccurs at 30mA, set by the 150ft resistor,and load changes up to this point causeoutput variations of at most 0.2V. Since thevalve grid is connected to the output line,load compensation is very fast.

Most of the voltage is dropped by the valve;-only about 20V appears across the 317. Withmy prototype, a short circuit with output setto 200V causes no damage.M. McDermottLondon

U

Load0 -200V30mAmax

Parallel data multiplexer with RS232 interfaceData on up to 64 digital inputs can besampled and passed through an RS232 orsimilar serial port using simple interfacehardware. A byte is sent to the uart, thelowest three bits of which (receive -data linesRBR1_3) address one of eight 8 -bit ports. Oneclock cycle later DR goes low, resetting theDR flag and loading the uart for transmis-

Data rote clock

sion by pulsing TBRL. Eight bits of data fromthe 74LS373 selected by the decoder arethus transmitted back to the computer.

After 64 clock cycles 4040 output Q5 goeshigh which loads a second byte for transmis-sion by the uart. This second byte echoes theoriginal chip address and the parity errorflag. Hence each time a byte is sent to the

5V

4049

14 21 17 4047k

11-N1133ND MR RRC TRC

1

38

37

34

16

39

36

35

20

5

Line dr,ver/receivers

Vcc

6402CLS1

CLS2 DR

C RL

SFD

EPE TBRL

585

RR()

P1 RBR2

RR1

DRR

RBRI

RBRB

TRO 7BRi_ 8 PE

15 DR1>

5 V

4011

4013

CK p CL CL

uart, two bytes are returned; one containingthe input data and a second for errorchecking.

Details of serial buffers or bit -rate gener-ators are not given as these will depend onyour requirements.G. SullivSnRedditch, Worcester

CK a

4040

MR ao

26-33

Al

74 LS138

A2

E2 E3 f3

02

D174L5373

DO

D3 61

Expon;onto otter

74 LS313s

74LS373

oo

07

Do

74LS373

oo

07

07

ttinputs


(-CIRCUIT IDEASSerial outputA -to -D converterUsing a few c-mos i.c.s data from amultiplexed -output analogue -to -digital con-verter can be turned into an RS232 -typeserial bit stream. One channel of an ana-logue multiplexer is used to provide twoinputs to the three -digit a -to -d converter.The circuit is suitable for battery operation.

Data is transmitted at 9600 baud, eightbytes every 50ms. One counter/divider scalesoutput of a stable timebase and the othercontrols three analogue multiplexers. One ofthese multiplexers selects from eight inputsto encode serialized bytes representing oneb.c.d. digit.

1 1 0/1 0/1

L input -multiplexing indicator

switch -state indicator

23 22 21 2°

A second counter/divider controls theserialization and digit -select multiplexers toproduce a pattern of eight serial words.

100 1 10 1 100 1 10 1

input 0 input 1

Serialization and digit -select multiplexersinclude pull-up resistors at their outputswhich function as pull-up resistors for the3162 outputs. This feature, made possible bythe analogue nature of the 4051 multiplex-ers, eliminates the need for individual multi-plexers at each 3162 output.

Output from the digit -select multiplexerdrives the timebase prescaler CLEAR input sothat the counter pauses until the desireddigit appears at the 3162 b.c.d. outputs.

The converter performs a dual -slopeanalogue -to -digital conversion in approx-imately 5ms and then outputs the hun-dreds, ones and tens digits consecutively.Each digit -select line is strobed for about5ms. Each digit is available for much longerthan one byte time so the interval is filledwith stop bits.

Only three digits need to be sent todigitize each input but the binary counterdigit -select output has four states. Thefourth digit -select multiplexer input selectsthe ones digit which is transmitted after thetens digit to fill this extra byte time.

Alternatively an And gate feeding Ao,1digit -multiplex inputs could drive theserialization multiplexer inhibit input toprevent transmission of the extra serialcharacter. Input Y3 to the digit -select multi-plexer could then be grounded instead ofbeing connected to pin 3 of the 3162. Thespare section of the 4053 multiplexer couldform this And gate.

The sixth bit of the transmitted word canbe used to represent the position of a switch.Samuel EisenpressSanta CruzCalifornia

5V

Analogueinput

0-1V,10k

Analogueinput

0-1V

Digitselect

9

5k

t 8,

IlVdd12

Yo A

13VIA z

YOBCo 4053

Y18

SA SB Vee Vss

RS 232output

141 11 10 71 8

131 61 14 12 11

Gain Mode Vcc (fsc inadj sel

CA3162Offset}, Digit bCd

nu II sel 0/pGNO '10 1 100' in

15

12

15

16 5

7 5 4

mpxer

10k

T2 45760MHz

oscillator

121 15 14 13 16

Y3YO Vdd

Z C 0 4051

Int) Vee Vss A2 Ao

6 7 8

a

141

lea rVdd

9 101 11

4

Opt ionaiswitch input

3

9V

Stop/sta rt13 16

Y

Y5

Y6

YO Vdd

C D4051

(YotoY7 RS 232 data sources)

0-A2 Y6 Inh Vee Vss

11 10 9 2 6 7 8

Clock

C 0 4024

Vss

41 5 11 9 6 3

Inputselect

-4 B -16 -32 -64 -128

Clock C 0 4024Vdd

Clear

Complex filter using two i.csWhen feeding audio output directly into alow -power f.m. transmitter., severe intermo-dulation occurred due to h.f. out -of -bandproducts. This was particularly noticeableduring tape playback since residual biasnoise caused audible beat notes.

My requirement was for steep roll -offfiltering above 15kHz with a deep notch at19kHz to eliminate stereo -tuner multiplextone. This multiplex -tone and 3 -pole low-pass filter uses only two i.cs and mainlypreferred values. Its response is flat within0.5dB to 15kHz, - 24dB at 19kHz and -

68p

0k

20dB at 30kHz falling at 18dB/octave.A variation elminates the multiplex filter

and gives a four -pole low-pass response butattempts to combine four -pole responsewith 19kHz notch filtering foundered due tocomponent interaction. No doubt computermodelling could overcome this but out herein the middle of the Pacific Ocean we have torely on empirical solutions.Tim MasonRadio VanuatuPort VillaVanuatu

Input stage for 4 polelow-pass alternativeUses component valuesshown in brackets above


Maxwell's e.m. theoryrevisited

If Maxwell's theory is about to be displaced according tothe many words in this journal recently, we might take a nostalgic

look at it once again.

66 ack to basics," we said, "beforeexpecting a profound paradigmshift. You ought to know a little

about the accepted norm." If Maxwell'stheory is about to be displaced (no pun!)according to the many words in this journalrecently, we might take a nostalgic look at itonce again.

"You don't mean, er, those - curls andthings...?" Not directly, but the curls - andthe grads, divs, dels - do seem to remainunpopular with students, probably thereason is bad teaching again...

Yet the developed theory of electromag-netism still holds sway. If there are somephenomena such a theory does not explain,then any new model must explain all that hasgone before - plus the new aspects. At leastthat is the way Thomas Kuhn outlined thesituation..

But Maxwell remains a good model, dis-placement current and all. In saying this, Ihave mentioned a vital point. It is only amodel, a kind of template held up againstnature, as it were. If the picture fits, so welland good, we can predict some occurancesand design a few things and earn somemoney.

Is it true? That is not a relevant question.We don't really care if it is absolutely true, wecan never know that anyway. The point is,does it work? If yes, we go ahead and makeour name, or even earn the money... Scienceand technology is pragmatic, whether prag-matism (in William James's sense2) is out offashion or not.

For example, electrons - are they reallythere? Is displacement current real? A num-ber of people have become hot under thecollar recently (and not so recently), aboutthe 'truth' of these ideas. But they havemissed the point. Nothing is ever withcertainty proved in science and thereforeneither is the engineering based on it. It canonly be refuted, when it fails to produce thegoods. This time, Karl Popper' had a fewwords to say on the subject, albeit my limitedcomments are a only a brief scratch on thesurface.

WHAT DID MAXWELL SAY AND WHY?

When James Clerk Maxwell was at Edin-burgh University, he came into contact withthe philosopher William Hamilton. In the

'JOULES WATT'

cut and thrust of ideas, the relativity ofhuman knowledge held sway, becauseHamilton taught that we only know rela-tions between things - not much aboutthings in themselves. This links back to aKantian view. All this affected the youngMaxwell deeply.

At the same time, Maxwell came upagainst the strict teaching and acute ex-perimental methods of the physicist JamesForbes, which also impressed him. It leftMaxwell always aware that his theoreticalconstructs must be refinable in the fires ofexperimental verification - a view rare intheoretical physicists.

LINES OF FORCE

A little later, Maxwell deeply appreciated thework of Michael Faraday and one of his firstimportant papers4 on Electromagnetismwas his "On Faraday's Lines of Force" (1856).The 'mechanical' properties of the imaginarylines included the tension in length (whichexplained attraction) and their repulsionsideways (explaining repulsion itself). Max-well modelled these properties mathemati-cally.

This first paper was followed in 1861 bythe paper "On Physical Lines of Force',because in the meantime William Thomson,later Lord Kelvin, had been in lively corres-pondence with Maxwell, and between thepair of them they had noticed all the analo-gies between: stream lines in fluid flow, linesof heat flow, electric current flow lines, linesof force in electric fields and lines of force inmagnetic fields.

These analogy relationships give partialexplanations. They are models, but crossfertilise thinking about different branches ofphysical science. Yet they warn us not tothink electricity is really a fluid water, orreally like a state of heat flow agitation...

Further discussion, this time with Stokes,had Maxwell contemplating Stokes' workshowing that heat flow in a non -uniformcrystal had a direction A not always parallelto the direction of maximum temperaturegradients 0.

A= TO

where T is a tensor, describing the aniso-tropic crystal. Maxwell immediately appliedthe analogy to magnetism and distinguished

the two vectors which he called the "flow" Band the "force" H and realised that in ananisotropic magnetic medium (like some ofour modern ferrites), the lines of force wouldnot always be parallel to the lines of flux. Thedirect analogy in the electric case was flowlines of current density J, with the force Esetting them up.

The trouble is that generations of studentshave been perplexed by these two 'different'vectors B and H describing the same thing -magnetic field. You might have found thisbecause of bad teaching again and a glance atthese original papers often helps.

VECTORS

The analogies led Maxwell to discourse ontwo classes of vector functions existing ingeneral, fluxes and forces. A flux B is subjectto a continuity equation and is integratedover a surface. The picture is 'streamingacross'. A force P is a vector which is usuallyderived - but not always - from a singlevalued scalar function, the potential and isintegrated along a line. It gives the concept'force along'. The vectors B and J are fluxes,H and E are forces.

In Maxwell's earlier discussions and grow-ing mental pictures, he stuck to three-dimensional Cartesians (the x,y, z axes). Butby 1870 after much correspondence withPeter Guthrie Tait and William Thomson,Maxwell' himself advanced the ideas ofconvergence (negative divergence), the curland slope (later called the gradient). Theextract from his paper is interesting:

. . Va has, in general, also a vector portion,and I propose, but with great diffidence, to callthis vector the Curl or Version of the originalvector function.

It represents the direction and magnitude ofthe rotation of the subject matter carried bythe vector a. I have sought for a word whichshall neither, like Rotation, Whirl, or Twirl,connote motion, nor, like Twist, indicate ahelical or screw structure which is not of thenature of a vector at all."

\ 1 /t \ 1 -. \

....... ........0 / I

Convergence Curl Convergenceand curl


Maxwell found Tait's enthusiasm for 'qua-ternions' invented by William Hamilton (notthe philosopher, but another Hamilton, themathematician), had given him the germ ofvector analysis - especially via the use ofHamilton's operator V. There was muchhumour in Maxwell's correspondence aboutV and his play on words regarding thepossible names for it: Nabla. or even Atledhad been suggested'.

Maxwell did not fully adopt the compli-cated quarternion ideas, but used the form,

d d

=jai+jzi+ k-dx

and realised the vector properties of it inconnection with the 'div' and 'curl' opera-tions. It remained to Willard Gibbs in apamphlet and Oliver Heaviside to oust'quaternions' but to bring in the full modernvector analysis notation. You will still find itmost entertaining to read Heaviside's pithycomments about Clarendon type faces andother notations. Maxwell and certainlyHeaviside would immediately recognise ourmodern presentation of the equations.

Advancing an argument started by Thom-son, Maxwell showed that any flux vector hadtwo parts. It had a component from the curlof a force vector plus another part which wasthe gradient of a scalar function. Formagnetism he wrote,

B=curlA + gradlif

and went on to say that in the absence ofmagnetic poles (or isolated magneticcharge) there are no sources and thereforegradll =O.

Therefore he had obtained a complete setof equations between B, H, J and E. At thisstage, still using Cartesian mathematicalarguments, Maxwell showed Faraday's elec-tromagnetic induction is described in ourmodern notation by,

curl E= - aB

and from this, by using B = curl A showed

aA aAcurIE=curl(-at) or E= - -at

Maxwell called this new function A the"electrotonic state" in recognition of Fara-day's speculations about a hypothetical stateof stress that must surround electrically ormagnetically 'charged' bodies.

STRUGGLES WITH MECHANICALANALOGIES

You will find Maxwell's struggles with howthe fields extend around the sources con-tained in the second "lines of force" papers.He tries analogy again with a kind of mecha-nical vortex model, see Fig.1. He extendedthe model from matter to space, postulatingan ether to contain the vortices. Considerthe array of vortices embedded in an incom-pressible fluid. When they rotate, centrifugalforces cause them to contract longitudinallyand they exert radial pressure. This is exactlyFaraday's proposal about the properties oflines of force.

But the concept drove Maxwell to see thatelectricity was not confined to a fluid in the

Maxwell's Figure 2 in his paper, "On Physic-al Lines of Force". The electric current wasrepresented by the 'ball bearings' runnirgfrom A to B and the resulting vortex moticnwas given to the imaginary 'cells' in thesurrounding space as shown. The line p toq shows what would happen if anotherconductor was placed along there, thusexplaining induction. One or two of therotation direction arrows are incorrect.

The flow lines of a current form closedpaths according to Maxwell. This meansthey must pass through the dielectric of acapacitor. including a vacuum. All thecurrent there must be in the form ofDisplacement or Electric Flux variations asno actual electrons are emitted throughthe region.

conductor on this view of things, but wasdisseminated in space - and the energy was'stored' in the space containing the fields...The function A, which we now call the vectorpotential, acted as a kind of momentumterm in the field. The equation E = aA/atwas equivalent to Newton's equation be-tween force and rate of change ofmomentum.

Now Maxwell hit upon the idea that themedium containing the vortices was elastic- hence the energy storage in the mediumwas by an elastic distortion. Two remarkableconsequences quickly follow. Since thespace surrounding a conductor is capable ofan elastic displacement - a varying fielddisplaces an equivalent current. This is thefirst glimmering of the "displacement cur-rent" postulate. Secondly, any elasticmedium with density p and a shear modulusm can transmit transverse waves with avelocity,

v= A rV P

Maxwell inserted magnetic and electric

quantities (based as we now say on permit-tivity and permeability) and found the wavevelocity would almost equal the thenaccepted value of the velocity of light. Withsome excitement he wrote in the "Lines ofForce..." paper

"The velocity of light in air, as determined byM. Fizeau*, is 70,843 leagues per second (25leagues to a degree) which gives

V=314,858,000,000 millimetres= 195,647 miles per second (137)

The velocity of transverse undulations in ourhypothetical medium, calculated from theelectro-magnetic experiments of MM. Koh-lrausch and Weber. agrees so exactly with thevelocity of light calculated from the opticalexperiments of M. Fizeau, that we can scarcelyavoid the inference that light consists in thetransverse undulations of the same mediumwhich is the cause of electric and magneticphenomena".

By 1865 Maxwell had written his paper "ADynamic Theory Of The EjectromagneticField"9. In it, he spelt out the full develop-ment of how the electromagnetic waveswould propagate. Note the word "field"appears for the first time in the title. He haddropped the "vortices" intermediate analogystage and relied on a few facts including thereally original concept of the 'displacementcurrent'. He effectively noted that themagnetic current is always a 'displacementcurrent' aBiat as there is nomagnetic chargein the Universe. Therefore why not some ofthe electric current at least in the formmat? The total current then, is alwaysclosed and is a set of flow lines

airJ'=J+at

where J' is the total current, J the conduc-tion current and aD/at is the displacementcurrent, D now being the electric flux ordisplacement vector. A changing currentmight set up a flow pattern in a capacitor likethat in Fig.2.

ELECTRICITY, MAGNETISM ANDLIGHT

Maxwell saw the significance of his con-struct. He wrote to his cousin, Charles Cay,"I have also a paper afloat, containing anelectromagnetic theory of light, which till I

am convinced to the contrary, I hold to begreat guns."

Again, the philosopher Hamilton's influ-ence on Maxwell in his youth can be seen.The build up via analogies, his developmentof the mechanical model - and then drop-ping it, and finally the analysis of the directrelations between the two classes of phe-nomena (magnetism and electricity) as aunifying structure - are all based on Hamil-ton's doctrine of the relativity of knowledge.Einstein said of Maxwell that he saw thefuture role of field theory in physics, com-plete with its describing differential equa-tions and seeing that was his stroke ofgenius.

The revolutionary idea is not really thedisplacement current proper, (in spite of theheat under many collars!), but the whole'dissemination' idea into the medium. Max-well's formal energy densities in the mediumwhich also link with some of Thomson'swork, encapsulate this view:


magnetic energy density =m

and electric energy density = D.E

Maxwell writing at the end of his "Dyna-mics..." paper, even calculated the peakvalue of the electric field in sunlight, both inthe solar constant at the Earth's surface andat the sun.

"The energy passing through a unit of area is

P2W-v

so that P=

where V is the velocity of light, and W is theenergy communicated to unit of area by thelight in a second.

According to Pouillet's data, as calculatedby Professor W. Thomson, the mechanicalvalue of direct sunlight at the Earth is 83.4foot-pounds per second per square foot. Thisgives the maximum value of P in directsunlight at the Earth's distance from the Sun,P=60,000,000, or about 600 Daniell's cells permetre. At the Sun's surface the value of Pwould be about 13,000 Daniell's cells permetre."

The model Maxwell gave explained andpredicted optical and electrical phenomenawith great vigour and precision. Whichevervectors you take, strictly transverse waves inspace appear because of the vector productnature of curl. The equations are the 'tele-graphers equations' of space, and look likethe transmission line equations Heavisidederived for waves on wires later:

apcurl H = + -at

aBcurl E = -t

div B = 0

div D = p.

with D = EE

B = 1.LH

J= crE

The wholly transverse solutions eliminatedthe longitudinal wave requirements that hadembarrassed earlier theories of light.

Heinrich Hertz's electrical generation anddetection of long maxwellian waves, with allthe predicted properties was a supremevindication. The vast proliferation of en-gineering uses of these waves up to thepresent time is a further supreme example.

PREDICTING POWER ANDUSEFULNESS BUILD UP

But just as important, Maxwell predictedthat the waves would exert a radiationpressure - thus disposing of the idea thatany luminiferous pressure would be a crucialargument for a corpuscular theory of light.Lebedev proved the radiation pressure post-ulate experimentally in 1900. It explains therepulsion of parts of the tails of comets. Suchradiation pressure is vital for Black Bodyradiation theory. It may be used to deriveclassically the time dilation formula of spe-cial relativity and explains how stars hold upinternally, together with their allowed massrange...

Maxwell's famous Treatise"' sets out theon -going work in book form, but adds little

more to his papers and memoirs. In the late1870s he was about to write a deeper inves-tigation into all these researches, but sto-mach cancer heralded his early death aged48 in November 1879 - at the prime of hispowers. As usual, we always speculate onwhat he might have achieved had he lived.

References1. T.S.Kuhn, The Structure of Scientific Revolu-tions Univ. Chicago Press, 1970.2. W.James, Pragmatism and Four Essays fromthe Meaning of Truth, Meridian Books, 1963.3. K.R. Popper. Conjectures and RefutationsR.K.P. 1972.4. J. Clerk Maxwell, On Faraday's Lines of Force,Scientific Papers, 1855, 1856, reprinted by Dover,New York, 1952.5. J.Clerk Maxwell, On Physical Lines of ForceScientific Papers, 1861, 1862.

6. J.Clerk Maxwell, On the Mathematical Classi-fication of Physical Quantities, Scientific Papers.7. Maxwell had much to say with Tait, Thomson,and many others via the 'halfpenny post' after thePost Office introduced it in 1869. Tait was knownas T' and Thomson as T'. These two authors wrotea "Treatise on Natural Philosophy" which wasreviewed by Maxwell - who henceforth referred toit as "T and r". Tait couldn't stand Tyndall,another scientist in the milieu, and referred tohim as r ('where r is a quantity of the secondorder...). Tait had written a book on Thermodyna-mics in which he had given an equation dp/dt=JCM. Maxwell then signed his cards:"...yourssincerely, dp/dt."8. 0. Heaviside, Electromagnetic Theory vol.l.chap3, The Elements of Vectorial Analysis andAlgebra, The Electrician 1893, Dover reprint.9. J.Clerk Maxwell, A Dynamical Theory of theElectromagnetic Field, Scientific papers.10. J.Clerk Maxwell, Treatise on Electricity andMagnetism, Oxford, 1873, 2nd. ed. 1881, 3rd. ed.1891.

Dividers faster than 3GHzBipolar devices offer better phase noise and speed powerperformance than gallium arsenide equivalents

Advances in semiconductor proces-sing and photolithography at Plesseyhave produced the first prescaler i.csfor frequencies above 3GHz. Theyincorporate silicon biploar transis-tors with 1.5p.m emitters and 7GHzf, at 0.5mW dissipation. Couplingthese transistors with 5µm -pitchmetal combines the high speed withhigh packing density.

Work is currently being done toincrease speed of the new dividers to6GHz, which will make them usefulfor applications like directly synthe-sizing local oscillators in C -band

satellite receiver front ends.Initially, the SP8800 prescaler

series consists of divide -by -two, four,eight and ten i.cs in surface -mountand dil packages. Sensitivity andoverload performances are good, asFig. 1 shows, and power dissipation/radiation are low. Being bipolar, thedevices inherently offer better phase -noise and speed/power performancethan GaAs equivalents.

Applications include counter pre -scaling and frequency synthesis. Fi-gure 2 represents a 3.5GHz frequen-cy synthesis loop with one of the newprescalers dividing by four and anSP8704 dividing by 128 or 129. Withthe world's first military -speci-fication 20mA 1.5GHz synthesizer,Fig. 3, it will be possible to produce atwo -chip military -grade frequencysynthesis loop.

The SP8850 is currently underdevelopment: samples should be

available in October.Nick Cowley

Fig.3

2 3

FREQUENCY (6Hz)4

Output 0 S to 3.5 6Hz Fig.2

Dual modulushigh speed

4 3 56Hz divider 5 nthesizer

Output 0.5 to 3 3 GHzH,gh speed divider

-4 33GHz /synthesizer

ELECTRONICS SZ WIRELESS WORLD 699

HfflouBliff ELS

LOW COST ELECTRONICS C.A.D.TV IF AMPLIFIER

7.:

IBM PC (and compatibles), RM NIMBUS, BBC MODEL B,B+ and MASTER, AMSTRAD CPC and SPECTRUM 48K"ANALYSER" I and II compute the A.C. FREQUENCY RESPONSE oflinear (analogue) circuits. GAIN and PHASE INPUT IMPEDANCE,OUTPUT IMPEDANCE and GROUP RELAY (except Spectrum version) arecalculated over any frequency range required. The programs are in useregularly for frequencies between 0.1Hz to 1.2GHz. The effects onperformance of MODIFICATIONS to both circuit and component valuescan be speedily evaluated.

Circuits containing any combination of RESISTORS. CAPACITORS,INDUCTORS. TRANSFORMERS. BIPOLAR and FIELD EFFECTTRANSISTORS and OPERATIONAL AMPLIFIERS can be simulated - upto 60 nodes and 180 components (IBM version).

RI no

t

A.N1,1(1.

Ideal for the analysis of ACTIVE and PASSIVE FILTER CIRCUITS. AUDIOAMPLIFIERS. LOUDSPEAKER CROSS -OVER NETWORKS. WIDE -BANDAMPLIFIERS. TUNED R F. AMPLIFIERS, AERIAL MATCHING NETWORKS. TV I F.and CHROMA FILTER CIRCUITS, LINEAR INTEGRATED CIRCUITS etc.

STABILITY CRITERIA AND OSCILLATOR CIRCUITS can be evaluated by-breaking the loop".

Tabular output on Analyser I. Full graphical output, increased circuit size andactive component library facilities on Analyser II.

Check out your new designs in minutes rather than days.

ANALYSER can greatly reduce or even eliminate the need to breadboard newdesigns.

Used by INDUSTRIAL. GOVERNMENT and UNIVERSITY R & D DEPARTMENTSworldwide. IDEAL FOR TRAINING COURSES, VERY EASY TO USE. Prices from£20 to £195.

Full AFTER SALES SERVICE with TELEPHONE QUERY HOT LINE and FREE update service.

0.a/Qgan,0

For illustratedillustrated leaflets and ordering information please contact Ref: WW

Crown Street. St Ives. Huntingdon. Cambs. PE17 4EB. Telephone: St Ives (0480) 61778

ENTER 42 ON 1 EPLY CARD

FORTH INSTRUMENTATION

COMPUTER

....0 ............

TT* - ................. - ---_____:-..... .....____ ..........

TITto.rii0

A powerful control computer based on the new Hitachi6303Y and high level language Forth. 100mm x 72mm.30K bytes RAM, 16K dictionary RAM 'PROM, 256 bytesEEPROM, 16K Forth. You can attach 64 key keyboard,LCD and PC bus peripherals. Built in are interrupts,multitasking, time of day clock, watchdog timer, fullscreen editor and symbolic assembler. 32 parallel and twoserial ports. Single power supply and low power 3mAoperational mode.

1 off £194.95 including manual and non-volatile RAM.

-/TDS9090

Triangle Digital Services Ltd100a Wood Street, London E17 3HXTelephone 01-520-0442 Telex 262284 (quote M07751

Toroidal &TransformersAs manufacturers we are able to offer arange of quality toroidal and laminatedtransformers at highly competitive prices

Toroidal Mail Order Price Listprices inclusive of VAT & Postage15va 7.95, 30va 9.18, 50va 10.16. 80va 11.36. 120va 12.07, 160va 14.20, 225va15.21 300va 17.04, SOOva 22.10, 625va 24.66. 750va 28.75, 1000va 44.82.Also available 1k2. 1k5. 2k. 2k5. 3k. Prices on request.

Available from stock the following voltages: 6-0-6.9-0-9. 12-0-12. 15-0-15. 18-0-18,22-0-22. 25-0-25 30-0-30. 35-0-35, 40-0-40. 45-0-45. 50-0-50. 110, 220. 240.Primary 240 volt.

Quantity prices and delivery on requestAir Link TransformersUnit 6. The Maltings, Station Road,

Sawbridgeworth, Herts. Tel: 0279 724425ENTER 26 ON REPLY CARD

IN VIEW OF THE EXTREMELY RAPID CHANGE TAKING

PLACE IN THE ELECTRONICS INDUSTRY, LARGE

QUANTITIES OF COMPONENTS BECOME REDUNDANT.

WE ARE CASH PURCHASERS OF SUCH MATERIALS AND

WOULD APPRECIATE A TELEPHONE CALL OR A LIST IF

AVAILABLE. WE PAY TOP PRICES AND COLLECT.

R. Henson Ltd.21 Lodge Lane, N. Finchley, London, N12 8JG.

5 mins. from Tally Ho Corner

Telephone: 01-445 2713/0749

700

ENTER 31 ON REPLY CARDENTER 25 ON REPLY (*AIM


APPLICATIONS SUMMARYDIGITAL SIGNALPROCESSINGSignal processing using analogue methods,where time and/or amplitude are con-tinuous quantities, has several disadvan-tages compared to digital methods wheretime and amplitude are discrete quantities.State-of-the-art analogue -processors areapproaching the limits of integration forsilicon and their parameters are difficult torepeat reliably in mass production: timeand temperature instabilities are also aproblem.

New digital -signal processorarchitectures increase processing speed. Se-quential processing (von Neumann) using asingle bus architecture, where instructionand data signals share a common path, hasbeen replaced by parallel processing (Har-vard). In Harvard architecture, instructionand data paths are separated. This enablesspeeds to be increased by pipeline processingin which several tasks can be accomplishedin a single instruction cycle.

Three stage pipelining (top diagram) isused with NEC's HPI)77230 to fetch aninstruction, execute an instruction and storeresults in parallel during a single 150nscycle. The 77230 advanced signal processorcan he operated in either master or slavemode (bottom).

NEC applications handbook 'Increase

KEY TO DIAGRAMS

Multiplier

FMPYK. LM

ALU

ALUEAUP.QSAC"'SHIFTSVRWRO-7PSW0.1WRTC

Floating-point multiplierFMPY 32bit data registersFMPY multiplication result

Arithmetic and logical unitExponent a.l.u.ALU/EAU date i/p registersShift and count registerBarrel shift registerShift value registerWorking registerProcessor status wordsWR transfer control

Data memories

RP Date rom pointerBASEO.1 Base pointersINDEXO.1 Index registersADD Adders

Instruction rom

PC Program counterSP Stack pointerIR Instruction registerDECODE Instruction decoder

Parallel interface

DPAPDRDRSARR/W CNT

Date portAddress portData registerSlave data registerAddress registerRead/write control

Serial tio interface

SOOSFTSICNTSIISFTSICNT

Control

INT CNTTRLCSR

Serial output registerOutput shift registerSerial o/p control reg.Serial i/p data registerInput shift registerSerial input control

Interrupt controllerTemporary registerLoop counterStatus register

number crunching capabilities: digital sig-nal processors' discusses the use of d.s.processors and applications includingnumerical control, speech processing, in-strumentation and telecommunications.

V00

VO 0-15CS

HROHWRROM

POP1P2P3

SLAVE

DO -D31 w v

AO -All

D

AP

RP

DATARAMO

512 W 32ba

ADD

BASH INDEXO

DATARAM1

512 W 32ba

ADD

BASE'' I I INDE >'

FMPY32bax321,1!

55ba

DECODE 1

INSTRUCTIONROM

2 KW x 32bet

R00.,

VVR

R/W CNT

ry

7

6

5

2

SP

SUB BUS

SOROo SOEN

OSFT SO

:1 SOCr,TSOCK

SCK-4

SICNT SICK

ISFr

ALU

WRO WR4WR1 WR5WR2 WR5WR3 WR7

cc

SIEN


APPLICATIONS SUMMARY

5n

80uH each oncommon core

9k1

t

141N4148

141N4148

>220k 2k2

2N5551

14

=IIM =IN. MEM MOM

100p I10N S1k3 I510p 1100n I10N

MC 34129

Ps ucontroller

illMTP2N20

1117107

22k

330p

01N5819100p

+5V

GNO

10k

(' 44 T1°°P1N5819

MOC 5007

-5V

Sync in

3k

10n

.5V

S1 Closed = on hookOpen-= off hook

MC145413

5V

5

16

15

14

13

8

1k 1620 1

7

10p

MC 34119

1t 75k 100k 10E -0-n-

5Vino ( Ii

01 1N4148 02 CO 1 4 1"\/\+-410

6 3 100kVcc FC1

GND FC2

TTMAll 100nm,..

Vdd.1--OC,-1

C3 E. " I

R1OSC L--i

I

10 500kHz

FIT) 11S2

I-4-4 Vss 6 eDTMF OH 12

ISO 0,'L 17

loon

0k 22k <22k5

47k

7k5

Handset

6

MC14403

16

wen

T0F

332

Rx0

Tx+1

vAG9

1° vLS

Tx

p/A

Tx]

Vdd

PDI

TDC

RDC

RCE

ROD

TDD

TDE

Vss

10k//560

100kN 3904

10k 10k I, 10k

100k

2 N 3904

100k2N39

Sync topower supply

12

13

MC 145 406

16

10 7

11 6

13 4

12 5

14 3

18 2

8 r-E-5v

20

17

14

2

11

+51/ MC145428

12

19

15

18

14

15

11

10

8

10

10p

-5V

13

Vdd

DOE

DIE

Tx0

Rx0

RxS

RST

DC

DCO

DC:

TxS

BRCK

DL 3

SB9

7

BR38

BC16

Vss

MC 145 4 26

+11502 vdd8 16

412

401 PD6 15

S:1 X17

CK13

14Tx

11Rx

19

12RE1

TE

00

o ,(;)o -oo

00 o

+5 VAllIA s-0-

5V

100n

22

11

096MHz

1/10M

L _ JS3 to S7

20p

20 p

10y /A .-- I-20

B

L02 s /VV\.,-.4 1

L --ir QLOI

21----t-'VV\i-'L 13 , 'WNW.

5VD

2

,...,

00n.I

i

.i.- mr

11Vss Vref

L100n Line transformer

00

TIP!

To psuiVin

I

T

Ring

_J



Digital voice/datatelephone setDesign of a digital voice/data telephone setis discussed in Motorola note AN968. Thistelephone set provides standard analoguefunctions while simultaneously transmit-ting 9600 baud asynchronous data from acomputer or terminal.

The voice/data i.cs used are from theMC145422/26 universal digital -loop trans-ceiver family. They provide 80kbit/s full -duplex synchronous communication over2km on one twisted pair. A pulse/tonedialler and c-mos RS232 i.c. for com-munication with a computer or terminalare included in the design and an efficientswitching p.s.u. provides an isolated supplyfrom the twisted pair's 48V.

Traditional tone signalling on the voicechannel is used. Looked at from the p.b.x..the voice/data multiplexer appears as anordinary telephone. The handset cradleswitch is replaced by a relay. S1, that openswhen the telephone is lifted.

Voice and data signals are converted todigital form compatible with the u.d.l.t. bythe 14403 codec/filter and 145428 data -setinterface respectively.

Ringing signal from the p.b.x. is de-tected, sampled and sent to the digitaltelephone where it feeds a loudspeaker

Connectionto externalterminal orcomputer

MC 145406RS -232 driver

receiver.,

M 1',

speakerdriver

MC14403

filter/codec

MC145428data -setinter face

Ring

sigral

through an amplifier. Analogue voice sig-nals are digitized and reconstructed by thecodec/filter duplexer which is linked to thep.b.x. wires via the u.d.l.t.

Asynchronous data to and from thecomput or data switch passes through thedata -set interface. Outgoing RS232 data issynchronized and sent to the u.d.t.l. full -duplex data channel at 8k bit/s. Conversionof incoming synchronous data to asynchro-

5

G ND

-5V

MC 1454'pulse/to,c

dialer

213516

7 619s0

ML 3,.129

switchingpower supply( isolated)

Line -interface

( transformerand=lion)

"141" ..^V;

it

nous form is also performed by the data -setinterface.

Direct current is applied to the twistedpair at the multiplexer and transputed overthe wires, so no extra supply lines areneeded.

Full constructional details are includedin the seven -page note. A further note,AN949, describes the voice/data multi-plexer.

Optimization of led operating conditions isdiscussed in Three -Five Semiconductor'snote No.1 . With low -voltage d.c. supplies,connecting a led is simply a matter ofcalculating an appropriate voltage -droppingresistor. Where the voltage drop is large orpower consumption is important, low -powerleds can be particularly beneficial.

With high voltage a.c. supply simpleresistive voltage -dropping elements arewasteful, can be physically large, and do nottake into account led reverse voltage. Thereare more efficient ways of driving leds froma high voltage a.c. source as this tableshows.

Also included in the note are equations forcalculating the voltage -drop elements andfurther information on each of the sixmethods.

+V Vmains

LED DRIVING CONSIDERATIONS

Supply 2.2V. V 0 6V 20mA standard led 10mA high efficiency 2mA low current Unit Light output

1 12Vd.c

R

Power dissipated4900.196

9800 098

49000.0196

11 Constant

2 240Va.c

IR


118602 37

593000.47w Pulsed 50Hz

3 240Va.c.

R


118904 76

594500.95

Pulsed 50Hz

4 240Va.c

R

Power dissipated118304 73

236602 37

118300047w Pulsed 100Hr

5 240Va.c.

C

Power dissipated0.533Negligible

0.267Negligible

0.053Negligible

F Pulsed 50Hz

6 240Vac

C

Power dissipated0.269Negligible

0.134Negligible

0 026 F

NegligiblewPulsed 100Hz

Vmoins Vmoins Vmoins

I®



3

470k

17

in

HLF 4001B

( I. in parallel)

17

150

14

BA 221

10k 1M1

4k7

C=lip

4 2V

-e

68k 36k5

BC 558

BC548 BC 548

VD=4 5V

1 M 90k9

Batterycheck

19k6

0 to 1V 1kfor digital

19k6 readouts

1k

Meter

Adjust C4 after half an houruntil meter reads 44%

Humidity sensor

Temp@ioiure C) 15 20 25

J "Potassium carbonate(K2CO3)

Battery poweredhygrometer

low-cost hygrometer running from a1000. 4.5V supply is one of five applicationsin the first VT & S Bulletin from Mullard.Electronic hygrometers are lightweight andeasy to maintain, operate and calibrate.Having electrical output, they are easilyinterfaced to other electronic equipment.

Capacitance of the dielectric -

foil sensor varies with relativehumidity. At 43% relativehumidity, the sensor is 122pFwithin 15% and its range is 10 to90% r.h. Frequency of one of thetwo RC oscillators shown is fixed:in the other oscillator. C of theRC network is the sensor so itsfrequency varies with relativehumidity.

Frequency difference between the twooscillators is translated into a pulsed voltagewith an average value proportional to themark/space ratio. This voltage appears at thebuffer i.c. output. Because the sensor char-acteristic is non-linear the average valuevaries non -linearly with humidity. A diodeand passive components following the bufferlinearize drive for the meter. pen recorder orled display.

For calibration. the sensor is replaced by a2% 118pF capacitor and the fixed oscillatorfrequency adjusted for minimum meter

Supply -voltage supervisorWhen a simple RC network controls thereset line of a microprocessor certain typesof power failure can result in incorrectresetting.

At power up the TL7705 supply -voltagesupervisor delays rising of the reset line untilsupply voltage is fully on. as does an RCnetwork. Unlike the RC circuit though, the7705 pulls the reset line low when supplyvoltage falls below 3.6V. When supply vol-tage rises above 3.6V, the reset line goes highafter a delay proportional to CT. Output isundefined when supply voltage falls below9v.

This circuit is from the Texas InstrumentsTL7705 applications sample available todesigners. A small p.c.b. and three passivecomponents are included in the kit.

Reset generator

8

RESIN RE' FT

REF

IC'T

VcC1

I

reading. This capacitor is then replaced by a

2% 159pF capacitor and the meter potentio-meter is adjusted for maximum meter read-ing. With the sensor in place, the variablecapacitor in the fixed oscillator is againadjusted until a known humidity is correctlydisplayed. Potassium carbonate in a sealedjar can be used for this. Operating frequencylimits of the sensor are lkHz and 1MHz.

Other notes in the VT & S Bulletin(varistors. thermistors and sensors) coverback-up lighting for fluorescent lamps atswitch on, colour tv e.h.t. supply protection,shaver -socket protection and using zinc -oxide varistors.

Addresses

Three -FivePO Box 131, Swindon.Wiltshire SN2 6XDTel. 0793 618835

NEC ElectronicsCygnus House.Sunrise Park Way,Milton Keynes MK14 6NPTel. 0908 691133

MullardMullard HouseTorrington Place

London WC1E 7HD01 580 6633

MotorolaITT Multicomponents346 Edinburgh Avenue,Slough.Berkshire SL1 4TUTel. 0753 824131

Texas InstrumentsOnline DistributionMelbourne HouseKingswayBedford MK42 9AZ0234 217981

FICreset networ7

I

10ke_s_xR SET'

'00n I M.

I T10P

5V

rocessor/computer

GNI],L _


Intermural tv signalsIt is sometimes forgotten that a simple half -wave dipole

correctly positioned can give a signal greater than the usualminiature indoor Yagi-t'da or log periodic antenna.

Television signals show regular stand-ing wave patterns of maxima insidebrick buildings. To investigate tyhe

usefulness of this effect I made measure-ments of the geometry and magnitude of thesignal pattern set up by the 0.51CHz radia-tion from the Sandy, Beds transmitter in abrick room at grid reference 761431. Themeasuring system comprised a half -wavedipole with a sleeve balun feeding a TESMC661C signal -strength meter.

Measured along a line parallel with they-axis the distance between successive signalstrength maxima was 42.7cm and, normalis-ing the peak signal amplitude to unity, theamplitude at the minima was 0.32. Resultsparallel with the z-axis were 24.0cm and0.75. These are sketched below.

At the position of minimum signal thedirection of polarization was that of theincident signal, approximately N -S. Awayfrom the minima it varied between direc-tions parallel to the y-axis and to the z-axis.

ANALYSIS

The observed signal patterns were tested forcompatibility with either a Fresnel or aFraunhofer diffraction pattern orginating inapertures formed by the irradiated walls.They did not fit either form but a system ofinterference between direct radiation in theroom and wall -reflected radiation was foundto agree with experiment.

Consider next, direct radiation alongd intersecting the once -reflected radiation rat the point la,b), as depicted next column.The geometrical path difference between dand r is 2cos O ID -b). Allowing for a IT phasechange on reflection the optical path differ -

Z4 32

0

0.75

42 7tm

0 24 Otm

ence is 2cos 0 ID - b) + X/2 where X is thewavelength of the radiation. For the point(a,b) to be a position of maximum signal

2cos0 ID - b) + X/2 = nA

where n is an integer. The separation invalues of b for successive maxima is then

(X/2) seal.

This is then the peak separation along thez-axis.

y

The reflected wave fails if the y -value of thepoint of incidence of r is negative, i.e. where

a<4 ID - ['flan°.

In addition, the optical path difference mustequal or exceed A for a maximum to bepossible and so

b. -5D- (X/41sec0.

Note that this maximum value for b will bevery sensitive to A if 0 approaches ir/2.

A similar analysis for radiation reflectedfrom the wall at y = W gives the peakseparation along the y-axis as

(A/2). tan 0. sec 0

This maxima pattern disappears if

a<W- B tan 0

Or

aL5W-(X/4)tan 0. sec 0.

Equating measured and analytical values forpeak separation along the z-axis gives

42.7=(A/21 tan 0 sec 0

and for the y-axis

24= (X/2) sec 0

whence

0 = 60.8° and A = 23.4cm.

The value of 0 agrees reasonably with thecompass value of radiation direction. Thefree -space wavelength A = 58.8cm and soXIA =2.5.

Moreno discusses the effect on wavelengthof the presence of dielectric material in an

enclosure showing, for microwaves, a valueof 1.5 for XIX with material having adielectric constant of 2.45. I suggest thatbrickwork shows a dielectric constant ofabout 7 for the 0.51CHz radiation underinvestigation, making the value of 2.5 forXIX reasonable.

lithe reflection coefficient of the wall is Rthen the intensity maximum is proportionalto (1-R) + R(1- R) and the minimum to(1-R) - R(1 -R). The ratio of maximum tominimum amplitude will be (1+ R)/(1- R).Thus for y variations:

max/min = 3.25 .*. R = 0.28

reflection angle = 90° - 60.8° = 29.2°.

For z variation:

max/min = 1.33 .*. R = 0.06

reflection angle = 60.8°

For radiation polarized normally to theplane of incidence the reflectivity should fallto zero when the incident and refractedangle add to 90°. If the incident angle is i andthe refractive index q then

i + sin '(sin = 90°

for zero reflectivity. As R falls from 0.28 withan incident angle of 29.2° to 0.06 at 60.8°,crude extrapolation puts R = 0 at an incidentangle of 69°, hence

69° + sin 2 Isin69/N ) 90°

making 11 - 2.6 and hence the dielectricconstant - 6.8.

This analysis assumes throughout thatthe incident wave is parallel to the ground,or approximately so.

DISCUSSION

At a maximum the internal signal intensityshould compare with the external value as((I -R) + 1211- R)):I. Taking the reflectivityR as 28% this ratio is 0.92:1 giving aninternal signal amplitude of 96% of theexternal magnitude. The introduction of alarge capture -area antenna into the enclo-sure must be avoided or the signal patternwill be disturbed and constructive interfer-ence lost.

If an analagous pattern were obtainedfrom the proposed satellite broadcasts itcould be exploited. possibly by a printedarray of linked dipoles with their size ad-justed to accord with the diminished inter-nal wavelength'. Such a system would avoidthe cost and aesthetic objections that roof -mounted dish antennas may generate.

I. Microwave Transmission Data. T.Moreno. Dover Pub-

lications. 1958.


[CIRCUIT IDEAS03 Q2 Q1 Q0 i/p o/p Q as a

functionof Q0

0

0

0

0

0

0

0

0

1

1

1

1

1

0

0

0

0

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

D0DoDIDID2D2D30304D4D5D5D6D6D7D-

1

0

0

0

1

1

0

0

0

0

RY generator forRTTY

QT)1

T)

QoQoQoQoQoQo

When designing hardware and software forRTTY reception it is useful to have a constantsource of RTTY data.

Three outputs from a clocked 4 -bit coun-ter feed A, B and C inputs of a multiplexer toselect one of eight inputs.

RTTY characters consists of at least sevenand a half units; a start bit, five data bits andone and a half stop bits. Using two stop bits,as with this circuit, does not cause problems.

Characters R and Y are usually used as atest message since they are complementary.For characters RY, the bit pattern is10010101 10101011. The counter's least -

significant bit provides the multiplexer datainputs.

As Q is a t.t.l. signal it can be used to drivethe input of the computer directly. To allow

L. 16

vca

ruR1 112

741S193

15 DO,

L004

R GNO

01

C1

16

3

2 9

6 10

11

116

Baud C1 R1

45.550

75

110

134

300

10p

3p3

3p310p

3p3

2p2

1k02k7

1k8

390

1k0

680

8

Shift Morkfreq.

C2

170

425

850

14451700

2125

1275

1272

1275

390n330n

pic

8200820o

150n 11c5

Vcc

A

B 113

74LS151

00

3

14

15

2

3

4

[Cu01

1 I4

Space

1275Hz

D2

Mark1445-2125Hz

560 1k

T 330n

47k

BC108

R6

0-1A.Mee-0

5.

560

R5 <1k C4 100n

testing of the terminal unit, two spare Nandgates provide mark and space frequency;Values of R2 and C2 determine frequengshift. Each oscillator is enabled by Q and Q

Phase -check pulse generatorWitches -hat pulses like those often used toindicate phase on circuit diagrams are im-mediately obvious on an oscilloscope screen,unlike narrow rectangular pulses where theedges tend to disappear.

Low impendance output is provided by aunity -gain buffer: pulses produced are atlkHz with a peak level of 1V.D.R.C. SelfLondon.

10p

--VV\ -0--10k

1V

111.,

Witches hot

22k Op -amps ore TL 074 or TL07 2

Diodes are general purpose silicon

outputs from the multiplexer.Mixing of mark and space frequencies is

done with a simple transistor Nand gate builtaround D1, D2 and Q1. Output is low-passfiltered by R6 and C. Reverse sense RTTY isobtained by swapping over Q and 0-multi-plexer outputs.P. HarrisonLichfieldStaffordshire

pulses

Output

6E17

(1.

9V-rPower

to op-omps _L9V


Universal voltage -

controlled oscillator withlow phase noise

An analysis of noise behaviour for a variety of v.h.f. transistorsshows that a j-fet produces the lowest phase noise.

For use in a v.h.f. synthesizer, a voltage -controlled oscillator was required withlow phase noise. The design was to be

such that only the mounting of a suitable tankinductor would guarantee operation at anycentre frequency in the band between 10 and300MHz. As there is no general agreement onwhich kind of transistor provides the lowestnoise in oscillators, the effect of transistornoise was investigated both theoretically andexperimentally.

In the general v.c.o. circuit of Fig.1, themost suitable frequency determining elementis an LC resonator electronically tuned byvariable -capacitance diodes. The drawback isthat the frequency is a non-linear function ofthe voltage, which results in the conversion ofamplitude into phase noise. The same phe-nomenon occurs in the internal capacitancesof the semiconductor devices in the amplifier.This counteracts the reduction of the phasenoise normally expected when the oscillationamplitude is increased. Therefore there issome optimum oscillation amplitude forminimum phase noise. This explains thenecessity of the amplitude control in Fig. I.

So that the oscillation -sustaining amplifierdoes not affect the resonator Q. its input andoutput resistances should be much higherthan the resonator resistance R.. Hence theamplifier can be modelled as a voltage -controlled current source. which is character-ized by its large -signal forward transconduct-ance Win). The oscillation amplitude is

determined by

1 - SIN/in) Zrdn = 0 ( 1 I

where n is the voltage transformation ratio ofthe resonator. The large -signal transconduct-ance can easily be determined graphicallyfrom the V -I transfer characteristic of theamplifier. This is shown in Fig.2 for anamplifier with a single transistor. For a stableoscillation amplitude, it is necessary that S is adecreasing function of V. This is generallynot the case for a single -transistor amplifier,apparent from Fig.2, at least not if the inputdirect voltage of the transistor is constant orcannot change very fast (within a few periodsof the oscillation). The oscillation amplitude isfinally limited by the supply voltage. This is tobe avoided, however, because the transistorimpedances will, in part of the oscillation

A. DEKKER

Z res

Resonatorn1

%%op

Sustainingamplifier

Gaincontro,

Bufferamplifier bout

Fig.1. Non -linearity of semiconductor junc-tions results in conversion of amplitude intophase noise which counteracts the reduc-tion of noise due to increase in amplitude -hence the need for optimization. Oscillationamplitude is related to transconductance(see text), obtained graphically from V -Itransfer characteristic, Fig2.

period, be very low and strongly non-linear,resulting in increased phase noise.

This was the main reason to use a differen-tial amplifier. Its large -signal transconduct-ance decreases with increasing input ampli-tude. Fig.3. at least if it is greater than theinput offset voltage. In addition, the input andoutput impedances of a differential amplifierare high, also when its output current satu-rates. Furthermore, the differential amplifierdoes not invert the phase, so that the resona-tor needs in principle no tap or coupling loop.

NOISE CONTRIBUTED BYSUSTAINING AMPLIFIER

The basic oscillator circuit is shown in Fig.4with fets. but bipolar transistors could also beused. The noise of this circuit has beenanalysed Iref.1) under the assumption that theparasitic capacitance C, of the source biascircuit has been compensated by the capacitor

VI V2 Val

C (ref.2). The result is the well-known for-mula

FkT f (2)PQM/

where F is the noise figure of the amplifier. fthe frequency of oscillation. P,, the available


Fig.3. Unlike a single -transistor amplifier a differential amplifier has the virtue thatlarge -signal transconductance is a decreasing function of input voltage.

I

tulip

Fig.4. Basic oscillator uses fets. though bipolar types could be used. which turn out toproduce a lower phase noise by as much as 10dB.

resonator power V2/812, and c is a factordepending on the amount of a.m. to p.m.conversion, which equals 0.5 for low oscilla-tion amplitudes V and 1 for the optimumvalue of V. The noise figure F for thedifferential amplifier is

I + for V < Vm 11 +c for Vo VmIbV

1.)swhere b = 0.5 for bipolar transistors and b =1.5 for junction fets, Vm is defined in Fig.3 andcan be considered as the maximum inputamplitude for which the amplifier workslinearly, and is the phase shift of the amplifer.Base and input resistances of the bipolartransistor have been neglected. The formulaapplies for a resonator transformation ratio of1 and it has been shown that this ratio isoptimum with respect to phase noise.

Formula 3 predicts that the lowest phasenoise can be obtained using junction fets: for adifferential amplifier with junction fets, Vm istypically 1 to 2 volts, whereas for a differentialamplifier with bipolar transistors Vm is only50mV. This accounts for some 10dB differencein phase noise.

131

NOISE CONTRIBUTED BY BUFFERAMPLIFIER AND CURRENT SOURCE

Current noise injected into the resonator bythe buffer amplifier is amplified with theoscillator closed loop gain 1/( I -S Zrejn) andshould thus be kept as low as possible. Voltagenoise is of minor importance, since it does not

enter the oscillator. It only produces a noisefloor which could raise the phase noise farfrom the oscillation frequency.

The input noise current density of both abipolar transistor and a junction fet is pro-portional to gn,Ifif1I2 for high frequencies.with gm the low frequency forward transcon-ductance. The best input device for the bufferamplifier is thus a low gm junction fet withhigh transition frequency. The buffer inputcapacitance which loads the resonator isnon-linear and may be lossy at high frequen-cies, and so it should be minimized. A sourcefollower loaded by the high input impedanceof an emitter follower keeps the influence ofthe gate -source capacitance low because thereis no significant r.f. voltage across it. Theemitter follower can provide the output powerto drive e.g. a 50ohm line.

Current noise injected into the resonatorcan be further reduced by taking the bufferinput signal from the sources of the oscillatortransistors.

If the collector of a bipolar transistorproviding the tail current of the differentialamplifier is coupled directly to the sources ofthe oscillator transistors, half of its currentnoise will enter the resonator. This noise canbe an order of magnitude higher than thecurrent noise of the oscillator transistors andwould therefore significantly increase thephase noise. The tail current source shouldtherefore be carefully isolated from the oscil-lator circuit for high frequencies. The isola-tion also eliminates an extra non-linearcapacitance in the oscillator circuit and soreduces a.m. to p.m. conversion.

EFFECTS OF 1/1 NOISE

Low frequency noise, in particular Uf noise.modulates the transconductance and junctioncapacitances of the oscillator transistors andso causes amplitude and phase noise. Theamplitude noise is further converted intophase noise in the voltage -dependent junctioncapacitances.

The use of low frequency feedback de-creases the noise in the collector or draincurrent and so the transconductance fluctua-tions. Further, the gate or gate bias circuitshould have a low impedance at low frequen-cies. In bipolar transistors, the la noise sourceworks in parallel with the base -emitter junc-tion current noise source and therefore theeffect of low frequency feedback by an emitterresistor is limited. The noise suppression isalready nearly maximal for an emitter resistorequal to the absolute value of the totalimpedance of the base circuit.

In theory, the effect of transconductancefluctuations could be reduced by high fre-quency resistive feedback in the sources oremitters. This didn't work in practice, prob-ably because of the phase lag and signalleakage to ground caused in combination withthe parasitic capacitances.

It is often assumed that fets produce moreUf noise than bipolar transistors. But ourexperiments showed the lowest phase noisewas consistently achieved using fets. Apartfrom the inherently lower high frequencynoise of fets in oscillator circuits, the lowerphase noise could also be caused by the weakdependence of transconductance on draincurrent, which reduced the effect of Uf noise.Furthermore, bipolar transistors with low IAnoise often have a high base resistance and aretherefore not usable in v.h.f. oscillators.

Other sources of Uf noise are the transistorproviding the tail current to the differentialamplifier and the amplitude control circuitdriving it. Tail current fluctuations causeamplitude noise, which is also converted intophase noise. Experiments showed that ingeneral the lowest phase noise was obtainedby shorting the low frequency tail currentvariations with a large electrolytic capacitor.Only if the oscillator transistors themselvesproduced a large Uf noise, was it favourable tomake the amplitude control loop fast, so thatthe large amplitude noise of the properoscillator was suppressed.

MINIMIZATION OF AM -TO -PMCONVERSION

The voltage dependency of the junctioncapacitances causes a.m.-to-p.m. conversion.The non -linearity of each junction capaci-tance should therefore be compensated by thenon -linearity of another one at which the r.f.voltage is equal. but in antiphase. The gate -

drain capacitances of the oscillator transistorsare automatically linearized, since they areanti -parallel.

The gate -source capacitances are in anti-series, and thanks to the compensation capa-citor C's their voltages are opposite. Theelectronic tuning of the oscillator is accom-plished by two matched varactors in anti -

series, where any asymmetry in parasiticcapacitances should be compensated.


OPTIMUM RESONATOR IMPEDANCE

The oscillator phase noise is inversely pro-portional to the resonator power, which inturn is inversely proportional to the resonatorimpedance, which should thus be made as lowas possible. There is, however, a bound belowwhich decreasing the resonator impedancedoes not improve any more or even deterio-rates the oscillator c.n.r. This is caused byseveral factors:

- At too low a value of the resonator impe-dance the oscillator transistors can nolonger provide sufficient output power.

- The I/f corner frequency of transistors in-creases with drain or collector current.

- Due to the base resistance of bipolar transis-tors, the equivalent input noise voltagecannot be decreased below a certainthreshold and will even increase when thecollector current gets too high.

Then there is the practical problem of decreas-ing the resonator impedance while keeping asufficient electronic tuning range because thecapacitance variation of v.h.f. varactors is

limited. The impedance could be transformeddownward by coupling the resonator via a tapto the oscillator circuit. This increases,however, the r.f. voltage to the varactors andso the a.m.-to-p.m. conversion.

CIRCUIT DIAGRAM

The circuit diagram of Fig.5 needs littleexplanation. Oscillation frequency is deter-mined by k, C3, C4, Di and D2. Resistors R1and R2 provide low frequency feedback toreduce the noise and the input offsetvoltage of the differential amplifier. Theiroptimum value is a compromise between I.1.feedback and amplitude control range. Cou-pling capacitor C9 has a low impedance at theoscillation frequency, but forms practically anopen circuit at low frequencies. Components

L2 and C5 prevent the r.f. noise of Tryentering the oscillator and C6 shorts thetransistor I.f. noise. The low -frequencydecoupling capacitors are connected to thepositive supply voltage to prevent modulationof the drain gate capacitances by noise on thepower supply.

Capacitor values of C1 and C4 are of theorder of some pF. They balance the voltagesacross the gate source junctions of the dif-ferential amplifier and across the varactors, toreduce a.m.-to-p.m. conversion. Besides, C1improves the frequency response of the ampli-fier.

To change frequency by a large amount 1.3,121 and R2 are the only components that needto be replaced. If the electronic tuning sensi-tivity is not critical, the oscillator can be tunedwith C1 over more than one octave.

PHASE NOISE MEASUREMENTS

The phase noise of the oscillator of Fig.5 wasmeasured using several types of transistors inthe differential amplifier. The place of the tapon the resonator coil and the amplifier tailcurrent were experimentally optimized forlowest phase noise. The results are shown inthe table.

The Table shows that the lowest phase noise

0+Vg

o Amplitudecontrol

Fig.5. To change frequency by a logic current, the only components to be charged are L3 andR1, R2. As it stands, it can be tuned over an octave with C3.

can be obtained with junction fets. Besides.the phase noise of an oscillator with fetsturned out to be less sensitive to the place ofthe resonator tap and the amplifier tail cur-rent.

TABLE 1. Lowest phase noise obtained at oscillation fre-quency of 100MHz at 5kHz from the carrier for severaltypes of transistors in the differential,amplifier.

Transistor Remarks2N3823 v.h.f junction fetBF198 v.h.f. bipolarCA3127 v.h.f. bipolar arrayBCY59C low I/f noise bipolarBFR90 low noise widebandBFQ69 low noise wideband

£(5kHz) (d8c/H4-116-106- 105- 91- 80- 70

The phase noise of the oscillator with the2N3823, BF198 and CA3127 was close to thevalue estimated with equations 2 and 3. Thehigh noise of the BCY59C is probably due to itshigh base resistance. The extremely highphase noise obtained with the BFR90 andBFQ69 is caused by a.m.-to-p.m. conversionof amplitude noise generated by l/f noise. Byincreasing the speed of the amplitude controlcircuit, the phase noise was reduced to-90dBc/Hz.

References1. Dekker. A. P.: Approximate noise analysis of afeedback oscillator using a non-linear differentialamplifier, to be published in AEU (Electronics andCommunication. Fed. Rep. of Germany).2. Dekker, A. P.: Compensation of parasitic sourcecapacitance in a fet differential amplifier. Letters.vol.22, no.I7, 14 Aug. 1986. pp.885-886.

A. P. Dekker is now with Nokia Telecom-munications, Espoo. Finland. having com-pleted this work at the Dr Neher Laboratoriesof the Dutch P7T. Leidschendam.

Non -switchingclass B amplificationFrom page 742

Under nulling condition. y = x + z. and afterelementary trigonometry:

132 = A' +

e = arctan (C/Al.

Now as only the output and the error signalare recorded. substitute A2 = 132 - C". Sofinally

e = arctan

Appendix 2 - Experimental amplifierTo eliminate influence from other distortionmechanisms as much as possible carefulcircuit design and layout were needed. Sepa-rate power supplies for the voltage gain stageand power stage were used and high currentground was separated from the signalground (see ref. 131. Test equipment groundwas connected to the input signal groundexcept for Fig. 8 recording, where the wholetest set-up was floating and the test amplifier"live" output was connected to the transientrecorder ground.

The voltage gain stage was designedaround a high performance operationalamplifier to simplify control over the open -loop bandwidth and gain, which were chosento represent typical values found in modernpower amplifiers.

Bias control was designed to be variableover a wide range to achieve requirementsfor class B and class A bias. The circuit mustbehave as a symmetrical low -impedancevoltage source for the output stage. ClassNSB operation was achieved by opening thecontacts of Sla and Slb and adjusting thequiescent current to the same value as theone chosen for class B operation. Class Aquiescent current was set to three amps.


Modelling Yagi antennasA suite of Pascal programs calculates the gain, terminalimpedance, current distribution and radiation pattern of

moderate -size Yagi-Uda antennas for any geometry, elementthickness and operating frequency.

In any antenna problem one is presentedwith a piece of metal in space with somekind of transmission line connected to it.

In the metal there will be currents flowing,and in the space surrounding it there will beelectric and magnetic fields. These may bethe result of a signal fed via the transmissionline, or the result of an incident field from adistant transmitter; in either case the cur-rents and the fields are unknowns whichneed to be found.

Maxwell's equations give the informationrequired to proceed. Firstly they allow cal-culation of the electric field anywhere inspace resulting from a specific current dis-tribution. Secondly, they require that thevalue of the total electric field tangential to aconductor is zero. The conductor can bethought of as providing a short circuit to theelectric field. From these two conditions itfollows that if the current distribution on theantenna is known and the tangential electricfield is calculated anywhere on the antennasurface. then we will get minus the incidentfield.

In this form the problem becomes that offinding a function of space which, whencertain mathematical operations are per-formed on it. give a specified answer. Oneway of tackling this is to approximate theunknown current function by a large num-ber of point currents of unknown amplitudescattered over the metal surface. Clearly, ifan infinite number of points were taken, theactual current could be represented exactly.But a sufficiently large number will give areasonable approximation. Suppose alsothat instead of insisting that the field is zeroeverywhere on the metal, we insist that it bezero on a large number of selected testpoints scattered over the surface. Thesepoints could be, but do not have to be, thesame as those at which the point currentswere located. One could not evaluate thefield at each test point resulting from eachpoint current source and set each one tozero. This would result in a set of simul-taneous equations from which the ampli-tudes of the point current sources could becalculated. The value of the current betweenthe points could be found by interpolation.Thus the problem is solved.

In practice this method, known as pointmatching, will work if the number of pointsis high, which means that a very large arrayof simultaneous equations has to be solved,resulting in the requirement for much com-puter storage and processing, and the likely-hood of significant rounding error.

C.J. RAILTON

The method can be improved by usingother approximations for the current. Sup-pose, for example, that the current on a wirewere expressed as a truncated Fourier series.Suppose also that instead of using testpoints, weighted averages of the field arecalculated over areas of the antenna and setto zero. The result of evaluating the simul-taneous equations would then be the Fouriercomponents of the current from which thecurrent anywhere on the metal could beevaluated. By doing this, accurate results areobtained with smaller systems of equations,but the calculation of each coefficient of thesimultaneous equations becomes morelaborious.

The way in which the current is expressedas a combination of known functions, suchas impulse functions or trigonometricalfunctions in the above examples, is referredto as expanding the current in a set of basisfunctions. The way in weighted average ofthe resulting field is taken is referred to as atest function. Clearly we have completefreedom as to what functions to use, and intheory they will all give the same answer. Inpractice, it is crucial that a good choice ismade; the penalty is a great deal of computa-tion and an inaccurate answer.

In the computer programs described, thebasis functions and the test functions are thesame. Each wire on the antenna is dividedinto segments, and the current in eachsegment is approximated by a suitable func-tion. The greater number of segments speci-fied for each wire, the more accurate will bethe answer, and the greater the computationtime. The points at which the antenna isconnected to a transmission line must be inthe centre of a segment. In the usual case ofcentre feeding this is no disadvantage. It isusually desirable, for best efficiency, tospecify more segments on the driven ele-ment than on those elements towards theends of the array. This is because greaterinaccuracy can be tolerated on those ele-ments carrying little current before thecalculated parameters are unduly affected.

GENERAL THEORY

Analysing any radiating structure consistsessentially of calculating the currents in theconductors and the fields surrounding themfor a given excitation. This excitation can bea current or voltage generator as in the caseof a transmitting antenna, or an incidentfield as in the case of a receiving antenna.

If the current distribution is known every-

where on the structure then it is compara-tively easy to determine the resulting scat-tered fields anywhere in space. This is doneby evaluating the following integral which isderived from Maxwell's equations:

Es(r)=1 (V2 + k2) G (r,r') (r') d3f' (1)

where Glr,r. I -expk( r - r')Ir-r'I

k= 27r/x

Determining the currents for a givenincident field, however, is not so straightfor-ward. To do this, use the fact that at thesurface of a perfect conductor the tangentialcomponent of the total electric field must bezero. Any incident field induces a voltageacross the conductor, and the resultingcurrent produces a scattered field whichexactly cancels the incident field on theconductor's surface. Since currents can onlyflow on conductors it follows that anywherein space the scalar product of current densityand the total electric field is zero. That is,

(E,(r) + Es( r) 1.1(r) = 0 (2)

where E, is the incident electric field and E,is the scattered electric field. Take thescalar product of both sides of equation 1with J(r) and substitute equation 2 intoequation 1:

i(V2+K2) (G(r.r1.110)..1(r)d3r'

= -E,(r).J(r) (3)

and the problem is to find a function J(r)such that this equation is satisfied for allvalues of r. Once we have managed to findsuch a function we know by the uniquenesstheorem that it is the correct solution. Acommon method of solving such equationsis the method of moments or weightedresiduals, a special case of which is used inthe computer program Calerkin's method.

The first stage in this method is to expressthe unknown current function J(r) as aseries of known basis functions .15(r):

oo

J(r) = 141,(r)(4)

Any permissible function J(r) can be repre-sented by an infinite number of coefficients


as provided that the functions 15(r) form acomplete set of functions that are non -zeroonly on the surface of a conductor. In theory,any such set can be used in the calculationbut, as we shall see, some choices yieldresults more quickly and more accuratelythan others.

A simple way of arriving at a set of basisfunctions which illustrate the technique isto divide the conductor surface into a largenumber of small areas. On each area therewould be one and only one non -zero basisfunction. Eact basis function would be non-zero on one and only one area where it wouldhave a value of unity. As the number of areasinto which the surface is divided increases,the real current distribution is more closelyapproximated. Such a set of basis functionswould be appropriate for a solid metal bodybut there are better sets available for a wireantenna.

Substitute equation 4 into equation 1 toget the following expression for the scatteredfield:

f (v2+ asG1r,r'1.1sle Id3r' = (5)

Since the basis functions are non -zero onlyon the surface of the conductors, multiplyboth sides of equation 5 by each of the basisfunctions, integrating over all space andmaking use of equation 2, gives

co

f( V2+ k2).as f Clr,r'11,(r)d3r d3r'

= -f 1,(r) d3r

r = 1 _cc. (6)

This is an infinite set of simultaneous equa-tions for the infinite number of unknowncoefficients, as, which determine the currentdistribution on the structure. In practice wetake a finite number of basis functions andignore the effect of the higher order terms ofthe sum.

With a good choice of basis functions, astends rapidly to zero as s increases so thatthis approximation will not cause significanterrors. For example, if the first term in theseries happened to be the actual distributionthen all the terms except the first would bezero. Conversely if the functions are badlychosen and the basis functions are verydifferent to the actual current distribution.then a large number of terms must beretained with the consequent increase ineffort, rounding error and the likelihood ofnumerical instability.

In fact, if we had multiplied equation 5 byany set of test functions which are non -zeroonly on the conductors then we would endup with a valid set of simultaneous equa-tions. If in addition the set of functions werecomplete, we could equally well proceedwith this new set of equations.

The choice of test functions, like thechoice of basis functions, is largely a matterof educated guesswork and experience. Thecase where the basis functions and the testfunctions are chosen to be the same isknown as Galerkin's method. For the prob-

2, 2, 7.

Fig.1. A single wire showing three overlap.ping piecewise sinusoidal functions. Cur-rent flowing in the wire is approximated bya linear combination of these three func-tions. The accuracy of the approximationcan be improved by using a greater num-ber of these basis functions.

R2

2

z3

Z,'Pi

R3

Fig2. E field at the point (Z,c) due to apiecewise sinusoidal current in the sectionof wire lying between points (z1,0) and(z3,0) is calculated using equations 9 and10.

lem under consideration (as well as manyothers) this choice leads to an efficientformulation.

Once a set of basis functions is decidedequation 6 can be solved, allowing calcula-tion of currents and fields in all space.

APPLICATION TO YACI-UDAANTENNA

The basis functions appropriate to a Yagiantenna must, from inspection of thegeometry, have the following properties:they must be zero everywhere except on thewires and they must fall smoothly to zero atthe ends of the wires.

Simple functions which have these prop-erties are the following:

sin(kiz- WI)js(z', sin(k1s/2)

on wire s

= 0 elsewhere

where Is is the length of the 5th wire z is thedistance measured from the centre of thewire.

This approximate current distribution iswidely used in published tables for the selfand mutual impedance of dipoles and forarray antennas. In fact this approximation isonly good if the wires are of the order of ahalf -wave long. For this assumed currentdistribution function, equation 5 becomes aset of simultaneous equations of order Nwhere N is the number of wires. Solution ofthis set would give the magnitudes of thecurrents on each element. Results for para-meters such as gain and impedance based on

this assumed current would not be accurate.but would give a rough idea.

A better approximation can be obtained byusing more than one basis function for eachwire, such as the following

sin k lz - zr, 11.1(z) - < z < zrsin k (zp - zis_11

sin k - z) z < z <sin k - zd P

(8)

where p=1 N zp = pl/In+1) - 1/2, I is thelength of the eh wire, and N the number ofbasis functions on the sth wire.

Here we are approximating the current onthe sth wire by dividing it into N overlappingsegments and specifying that each of the Nbasis functions are non -zero only on onesegment.

These functions are shown in Fig.1 for onewire. They form overlapping sinusoids thatgo to zero at the wire ends, as required by theboundary conditions. If N is chosen to be 1then we recover equation 7. As N is in-creased, the actual current can be betterapproximated, yielding a more accurateanswer at the expense of greater computa-tion.

We are at complete liberty to specify adifferent number of basis functions on differ-ent wires. Indeed, it is desirable to a specify alarger number of basis functions for thedriven element than for the others, especial-ly when calculating terminal impedance.

However, there is no guarantee that thesolution will improve as the number of basisfunctions is increased. Although we areensuring that the boundary conditions arebeing satisfied on the average in moreplaces, we are saying nothing about how wellthey are satisfied in any one place. It is quitepossible for the value of the calculated totalfield to oscillate widly about zero from placeto place and still satisfy equation 6. But inpractice, for sensibly chosen basis functions.Galerkin's method is well behaved.

Experience has shown that the piecewisesinusoidal basis functions given in equation8 are well suited to the Yagi problem. Inaddition. with this choice of basis functions.the integral of equation 1 is available as in asimpie closed form which can be expressedin cylindrical coordinates as follows:

E.expl-jkRi )

R1k1/2

expl-jkR2Isin kl exp 1-jk123)

R2sin2(kV1) R3sin (kl/2)1

(9)

j30 {(z- lexp-jkR+Ed, -

(I) Rizsin (kI/2)

+ -R2sin-lk1/2)

lz -z3exp-jkR3 1R3sin(k1/2) f

1101

where the dimensions are defined in Fig.2.

ELECTRONICS & WIRELESS WORLD 7 1 1

Fig.3. Polar radiation patterns of a 30MHz seven -element Yagi using wires of radius25mm.

28.5MHz- -

29MHz---

285MHz

29.5MHz

29MHz

(7',

1

\

30MHz

In the case of a Yagi all the elements areparallel and so we need only concernourselves with the z -directed field. Notheoretical difficulty would prevent exten-sion to elements placed at any desiredorientation if required.

Substituting equation 9 into 6 gives

142

fJr dz = f Ezi.1dz (11)

p S1,,r2

for q = 1...number of elements r =1...number of basis functions on the qthwire, and where 1, is the length of the rthsegment on wire q, Ez, is given in closedform by equation 9.

The integral is the mutual impedancebetween the segments rq and sp. Integrationcan be carried out numerically withoutundue trouble. The problem is now reducedto the evaluation of a number to calculatethe values of the coefficients and hence theapproximate current on the elements.

EXCITATION

30 5MHz 31MHz We now have a computation method whichallows us to find the currents on a Yagiantenna for a given incident field. To calcu-late useful parameters such as the gain andthe terminal impedance, it is necessary toconsider the incident field produced by atransmission line connected to the driveelement.

Various models for the feed point of anantenna have been used and they vary inaccuracy and complexity. A simple but effec-tive one is the delta gap. Here we assumethat the driven element has an infinitesimalgap at the driven point. Across this gap isapplied a voltage source such as a transmis-sion line. With this model, the integral onthe right hand side of equation 11 becomesequal to the magnitude of the voltagesources times the value of the test functionat the driven point.

tion of a real feed system, but it does giveClearly this model is only an approxima-

,C.- good answers and it is widely used.v Once the currents have been calculated by

means of equation 11, the terminal impe--dance is immediately given as the drive

30MHz voltage divided by the current in the drivensegment. To calculate the gain we need toknow the magnitude of the radiated field farfrom the antenna. For large distances equa-tion 9 and 10 become

j30 exp -jkRisin (kI/2)

30 5 M H z 31MHz exp (-1kR) sin kl exp -jkR31sin2(k1/2) sin (kI/2) I (12)

Fig.4. Polar radiation patterns of a 30MHz seven -element Yagi, this time with wires of10mm radius. E,b = E, tan (1) (13)


where F is the angle of elevation of thepoint of observation.

The gain is given by

(iEz12 + iEri2) Zo4 Tr P,

where Po, is the total power delivered to theantenna.

PROGRAM DESCRIPTION

The program is split into three parts, partlyfor reasons of space and partly from conveni-ence. It is possible to run the programs onmost computers which have a Pascal compil-er with very little change. The only machine -specific part of the program is the graphicsroutines which are written in Z80 machinecode. It is likely that equivalent graphicslibrary routines would be available on othermachines.

First of all, the program GETWIRES takesinformation from the keyboard about thegeometry of the antenna to be analysed. Itthen produces a file which is used by the nextpart. This avoids the need to type in thegeometry each time an analysis is to be done.

The actual analysis is carried out in theprogram YAGI which calculates the currentson each segment for a given excitation andfrequency. The radius of the wire used can bespecified, as can the number of segmentsinto which to divide each wire. In this waythe accuracy of the solution can be tradedagainst computer time.

The main procedures in the programperform as follows:GETIMP calculates the mutual impedance be-tween segments of specified length andposition at a given frequency and with theassumed piecewise sinusoidal current dis-tribution. This is carried out by numericallyevaluating the integral in equation 11. Func-tion F is the integrand, and the integral iscarried out by function cAusin by means ofthe gaussian quadrature method.CLUFAC and CLUSOLVE solve the set of complexsimultaneous equations represented by acoefficient matrix A and a vector B, the resultis given in a vector X.

UOSELF calculates the mutual impedance be-tween all segments on a particular wire andsets the appropriate elements of the matrixzMAT. Because all the segments on any givenwire are the same length and are placed

contiguously, only one calculation per seg-ment need be performed.

MOTHERS calculates the mutual impedancebetween all segments on a given wire with allsegments on another given wire and sets theappropriate parts of matrix ZMAT. Since, ingeneral, the segments on different wires canbe of different lengths, each value is workedout separately.

SETURWEN requests information about theexcitation of the antenna and stores theinformation in the structure URN.

DOANT calculates on each segment for aspecified excitation and frequency and calcu-lates the terminal impedance. For a two -element array the mutual impedance be-tween the wires is also calculated.

oirrcuRR saves the calculated currents for useby the program PLOTFIELD.

PLOTFIELD takes the information calculated byvac! and produces a polar of the far -fieldradiation pattern. By means of a screen copyroutine, the diagrams together with annota-tions can be printed onto a dot matrixprinter.

RESULTS

To show the sort of results which can beobtained from the programs two different

25mm !lows ..

10mm r00.u5

295 30FRETJEV.r

Fig.5. Gain as a function of frequency forthe antennas of Figs 3 & 4.

Fig.6(a) (below, left). Resistive part of theterminal impedance as a function of fre-quency, showing the effect of varying thewire radius.

Fig.6(b) (below, right). Reactive part of theterminal impedance of the seven -elementarray as a knction of frequency for wireradii of 25 and 10mm.

80-

60-70- \

55/40-

60- Z 20-/

a

ri; 0

cc50-

25mm radius -20-z

40-- F

..10mm radius-60--7030

285 29 295 30FREQUENCY (MHz)

3015 31

Yagis have been analysed. Figures 3 and 4show a series of polar diagrams for a seven -element Yagi with wire thicknesses of 25mmand 10mm respectively. Spacing is 3m.Reflector length 4.75m, driver length 4.55mand director lengths are 4.39m. Notice howthe radiation pattern breaks down as thefrequency approaches 31MHz.

Figure 5 shows gain plotted against fre-quency for this antenna and Fig.6 showsterminal impedance versus frequency. Theeffect of varying the element thickness canbe clearly seen. This antenna was analysed byThiele' for a frequency of 30MHz and wireradius of 25mm using a reaction matchingtechnique. The results for gain and impe-dance are in good agreement.

These results, especially the plots againstfrequency, are not quick to obtain and anovernight run is likely to be the norm. Theprograms have, however, been designed torun with little intervention so that thisshould not present a great problem.

PROGRAM EXTENSIONS

Any moderately -sized array of parallel wirescan be analysed by the programs as de-scribed. But it is possible to extend theprograms to cope with skew wires or bentwires such as a folded dipole or a cubicalquad. With different basis functions it wouldbe possible to analyse the effects of metalstructures in the vicinity of the antenna, asthe case of vehicle -mounted antennas.

References1. Antenna Theory and Design, by Stutzman and

Thiele, Wiley, 1981, p226.

2. Radio Communication Handbook, Radio Socie-ty of Great Britain. 1969. p14.22.

Enquiries about software described in thisarticle should be addressed to the author atCadney, Highfield Road, Whiteshill. Stroud,Gloucester GL6

Chris Railton is at the University of Bath.working for a Ph.D. on boxed microstripcircuits.

-

29

25mm radius

30 305FREQUENCY (MHz)

10mm radius


GiCOMPUTER WAREHOUSE1000's OFBARGAINSFOR CALLER

THE ALL/WINS CAVE OP COMPUTER AND ELECTRONIC EQUIPMENTMOT LIME DATA VASE

*DISTECPThe ORIGINAL FREE OF CHARGE dial up database. Buy, browse or place YOUR OWN AD forgoods or services to sell. 1000's of stock items,

spares and one off bargains Updated daily.ON LINE NOW. CCITT, 8 bit word, no parity.

For 300 baud modems call 01-679 1888For 1200-75 baud modems call 01-679 6183

FREEYOtli; monitor£29.95 of from its computed!becomesRFoBr

QUALITY COLOUR TV SETThe tabu,,, TELEBOX an INVALUABLE MUST for the owner ofANY video monitor with a composite input colour or monochromeMade by a major UK Co as a TOP OUALITY. stand alone UHFtuner and costing OVER £75 to manufacture. this opportunity togive your monitor a DUAL FUNCTION must not be missed. TheTELEBOX consists of a compact, stylish two tone charcoalmoulded case. containing ALL electronics tuner, power supply etcto simply plug in and convert your previously dedicated computermonitor into a HIGH QUALITY COLOUR* TV SET. giving a realbenefit to ALL the family.. Don't worry if your monitor doesn't havesound- THE TELEBOX even has an integral4 watt audioamplifierfor driving an external speaker PLUS an auxiliary output for superbquality television sound via your headphones or HI Fl system etcOther features include. Compact dimensions of only 15 75 w x7 5 d x 35 h latest technology. BRITISH manufacture fully -tuneable] channel push button tuner. Auto AGC circuit. SAW falter.LED status indicator, fully isolated 240v AC power supply for totalsafety. Mains ON -OFF switch etc Many other uses

LIMITED QUANTITY - DON'T MISS THIS OFFER!!

mum

DON'TDON'T MISS THE CPM DealOF the CENT RY rt

The FABUL U CPM TATUNG PC2000Professional Business System

A cancelled export order and months of negotiation enables us to offer this professionalPC, CPM system. recently on sale at OVER £1400. at a SCOOP price lust over the cost ofthe two internal disk drives" Or less than the price of a dumb terminal..Not a toy. the BIG BROTHER of the EINSTIEN computer, the DUAL PROCESSORPC2000 comprises a modern stylish three piece system with ALL the necessities for theSMALL BUSINESS, INDUSTRIAL, EDUCATIONAL or HOBBYIST USER. Used withthe THOUSANDS of proven, tested and available CPM software packages such asWORDSTAR, FAST. DBASE2 etc. the PC2000 specification. at our prices, CANNOTBE BEATEN"The central processor plinth contains the 64K, ZBOA processor, DUAL TEAC 55F 5','.

Double sided 40/80 track disk drives 11 Mb per driver PSU, 4K of memory mapped screen RAM. disk controller. RS232,CENTRONICS and system expansion ports and if that's not enough a ready to plug into STANDARDS" DRIVE port for up to FOUR8 disk drives either in double density or IBM format The ultra slim 92 key. detachable keyboard features 32 user definable keysnumeric keypad and text editing keys even its own integral microprocessor which allows the main ZBOA to devote ALL its time toUSER programs eliminat ing"lost character' problems found on other machines The attractive detachable 12' monitor combinesa green anti -glare etched screen with full swivel and tilt movement for maximum user comfort Supplied BRAND NEW with CPM2.2. user manuals and lull 90 day guarantee. Full data sheet and info on request

PC2000 System PC2000 Business System with CPMwith CPM Etc. and 'Ready to Run' FAST Sales and

COST OVER C1400 Purchase ledger, supports up to9000 Accounts. VAT etc.

COST OVER £1700Nily £399

ONLY £29.95 OR £24.95 if purchased with ANY of ourvideo monitors Supplied BRAND NEW with full instructions and 2 YEARwarranty l'Ost and packing £3 so When used with colour crt

COLOUR a MONOCHROMEMONITO r SPECIALS

'SYSTEM ALPHA' 14 COLOUR MULTI INPUT MONITORMade by the famous REDIFFUSION Co. for their own professional computersystem this monitor has all the features to suit your immediate and futurerequirements Two video inputs RGB and PAL Composite Video, allow direct standard RGB colour monitor Many other featuresconnection to BBC/IBM and most other makes of micro computers or VCR include Printer output Full keyboard input. Cassetteincluding our very own TELEBOX An internal speaker and audio amp may be port etc BRAND NEW with DATA A FRACTION OFconnected to computer or VCR for superior sound quality Many other featuresPIL tube, MatchingBBC case colour. Major controls on I ront panel SeparateContrast and Brightness - even in RGB mode Separate Colour and audiocontrols for Composite Video input BNC plug for composite input 15 way 'ID'plug for RGB input modular construction etcetc

This Must Be ONE OF THE YEAR'S BEST BUYS. PC USERSupplied BRAND NEW and BOXED. complete with DATA and 90 dayguarantee ONLY £159.00 asabove ORIBM PC Version el 65.00

5 Day 'd skt £1.00 BNC skt 75p BBC interface cable £5.50

NOW only £499Carriage 8 Insurance £12.00

f SURPLUS SPECIALS ONTPRESTEL - VIEWDATA - TELEX

DECCA 80 16 COLOUR monitor. RGB input.Little or hardly used manufacturer's surplus enables us to offer this specialconverted DECCA RGB Colour Video TV Monitor at a super low price of only£99.00. a price for a colour monitor as yet unheard of Our own interfacesafety modification and special 16 high definition PIL tube coupled with theDECCA 80 series TV chassis give 80 column definition and quality found onlyon monitors costing 3 TIMES OUR PRICE. The quality for the price has to beseen to be believed. Supplied complete and ready to plug direct to a BBCMICRO computer or any other system with a TTL RGB output Other featuresare imerna! speaker, modular construction, auto degaussing circuit. attractiveTEAK CASE. compact dimensions only 52cm W a 34 H a 24 D. 90 dayguarantee Although used units are supplied in EXCELLENT condition.ONLY £99.00 + CarriageDECCA 80 16 COLOUR monitor. Composite video input. Same as abovemodel but fitted with Composite Video input and audio amp for COMPUTER,VCR or AUDIO VISUAL use ONLY £99.00 + Carr.REDIFFUSION MARK 3, 20 COLOUR monitor. Fitted with standard 75 ohmcomposite video input and sound amp This large screen colour display is idealfor SCHOOLS. SHOPDS. DISCOS CLUBS and other AUDIO VISUAL appli-cations Supplied in AS NEW or little used condition ONLY £145.00 + Carr

BUDGET RANGE EX EQUIPMENT MONOCHROME video monitors.All units are fully cased and set for 240v standard working with composite videoinputs Units are pre tested and set up for up to 80 column use Even whenMINOR screen burns exist - normal data displays are unaffected 30 dayguarantee*12 KGM 320-1 B/W bandwidth input will display up to 132 x 25 lines £32.9512 GREEN SCREEN version of KGM 320-1 Only £39.959 KGM 324 GREEN SCREEN fully cased very compact unit Only £49.00

Carriage and insurance on all monitors E10 00

IYGOULD OF443 enclosed, compact switch mode supply with DC regulatedOutputs of +5v r 5 5a. +12v 0 5a. -12v 0 la and -23v - 002a Dim 18 a11 a 6 cm 110 or 240v input BRAND NEW only £16.95GOULD G6 -40A 5v 40 amp switch mode supply NEW £130.00AC -DC Linear PSU for DISK drive and SYSTEM applications Constructed on arugged ALLOY chassis to continuously supply fully regulated DC outputs of +5v

3 amps. -5v a. 06 amps and +24v 5 amps Short Circuit and overvoltageprotected 100 or 240v AC input. Dim 28 x 12 5 x 7 cm NEW £49.94

Carriage on all PSU s £3 00

I:4 TA IllYAI:P111 Manufacturer's BRAND NEW surplusDEC LA34 Uncoded keyboard with 67 quality gold plated switches on X -Ymatrix - ideal micro conversions etc £24.95AMKEY MPNK-114 Superb word processor chassis keyboard on single PCBwith 116 keys Many features such as On board Micro. Single 5v rail full ASCII

coded character set with 31 function keys, numeric keypad cursor padand 9600 baud SERIAL TTL ASCII OUTPUT'. Less than half price

Only £69.00 with data Carriage on Keyboards £3.50

PLESSEY VUTEL, ultra compact unit slightly largerthan a telephone features A STANDARD DTMFTELEPHONE stone dial) with 5 CRT monitor andintegral modem etc for direct connection to PRESTELVIEWDATA etc Designed to sell to the EXECUTIVE atover £600" Our price BRAND NEW AND BOXED atonly £99.00DECCAFAX VPI complete Professional PRESTELsystem in slimiine desk top unit containing Modem,Numeric ke pad, CPU. PSU etc Connects direct to

COST only £55.00ALPHATANTEL. Very compact unit with integral FULLALPHA NUMERIC keyboard. Just add a domestic TVreceiver and you have a superb PRESTEL system andvia PRESTEL the cheapest TELEX service to befound" Many features CENTRONICS Printer output.Memory dialling etc. Supplied complete with data andDIY mod for RGB or Composite video outputs ASNEW only £125.00

Post and packing on all PRESTEL units £8 50

EX -STOCK INTEGRATED CIRCUITS4164 200 ns 0 RAMS 9 for £11 4116 nsC1 50 2112 £1000 2114 £2.50 2102 £2006116 £2 50 EPROMS 2716 £4 50 2732 caoo2764 £4.95 27128 E5 50 6800 E2 50 6821 C 168A09 E8 68809 £10 8085A C5.50 8088 C158088 £8 NEC765 £8 WD2793 £28 8202AC22 8251 £7 8748 £15 Z80A DART £6 50Z80A CPU C ? 00 Thousands of IC's EX STOCKsend SAE

DIS D IVESJapanese 5'. half height, BO track double sided diskdrives by TEAC. CANON. TOSHIBA etcSold as NEW with 90 day guarantee ONLY £85.00TEC FB-503 Double sided HH 40 TRK NEW £75.00SUGART SA400 SS FH 35 TRK £55.00SIEMENS FDD100 SS FI-140 TRK £65.00carriage on 5'. drives £5 50Brand NEW metal 5'. DISK CASES with internal PSU.DSKC1 for 2 HH or 1 FH drive £29.95 +pp £4.00DSKC 2 for 1 HH drive £22.95 +pp f3 50DKSC 3 As DSK1 LESS PSU £12.95 +pp £2 50DSKC 4 As DSK2 LESS PSU £10.95 +pp £2008 IBM format TESTED EX EQUIPMENT.SHUGART 800/801 SS £175.00 +pp C8.50SHUGART 851 DS £250.00 +pp C8.50TWIN SHUGART851'62 Mb total capacity in smart casecomplete with PSU etc £595.00MITSUBISHI M2894-638' DS1 Mb equiv. to SHUGARTSA850R. BRAND NEW at £275.00 +pp E8.50DYSAN 8" Alignment disk £29.00 + pp £1.00Various disk drive PSU's Ex Stock SEE PSU section.HARD DISK DRIVESDRE/ DIABLO Series 30 2.5 Mb front load £525.00Exchangeable version £295.00. ME3029 PSU £95.00DIABLO 44/ DRE4000A, B 5+5 Mb from £750.00CDC HAWK 5+5 Mb£795.00. CDC 976280 Mb RM03etc £2500.00.PERTEC D3422 5+5 Mb £495.00RODIME 51/4 Winchesters ex -stock from £150 CALLClearance items- Sold as seen - No guaranteeICL 2314 BRAND NEW 14' Mb Removable pack harddisk drive cost over (2000 with data ONLY £99.00BASF 6172 8 23Mb Winchesters £199.00Unless stated all drives are refurbished with 90 dayguarantee Many other drives and spares in stock - call

sales office for details

PC2000 Wordprocessor Systemwith CPM and TEC FP25 daisywheel

printer

NOW only £799

MODEMSJoin the communications revolution with our superrange of DATA MODEMS prices and specificationsto suit all applications and budgetsBRAND NEW State of the art productsDACOM DSL2123 Multi standard 300-300. 1200-75Auto answer etc £268.00DACOM DSL2123A0 Auto dial, smart modem withmulti standard AUTO SPEED detect and data bufferwith flow control etc £365.00DACOM OSL2123GT The CREAM of the intelligentmodems auto dial auto call index, bufferetc etc f498.00Steebeck SB1212 V22 1200 baud FULL DUPLEXsync or async, optional auto dial £465.00TRANSDATA 307A Acoustic coupler 300 baud fullduplex, originate only, RS232 interface £49.00

Ex BRITISH TELECOM full spec CCITT. ruggedisedbargain offers Sold TESTED with data Will work onany MICRO or system with RS232 interface.MODEM 13A 300 baud unit only 2" high fits underphone CALL mode only £45.00_MODEM 20-1. 75-1200 baud Compact unit for useas subscriber end to PRESTEL. TELECOM GOLD,MICRONET etc £39.95 +pp C6.50MODEM 20-2 1200-75 baud Same as 20-1 but forcomputer end £65.00 +pp £6.50DATEL 2412. Made by SE Labs for BT this two partunit is for synchronous data links at 1200 or 2400baud using 2780/3780 protocol etc Many featuresinclude 2 or 4 wire working self test auto answer etcCOST OVER £800. Our price ONLY £1 99 +pp E8.00DATEL 4800, RACAL MPS4800 baud modern EXBT good working order, ONLY £295.00 +pp £8.00

SPECIAL OFFERMODEM TG2393. Ex BT, up to 1200 baud fullduplex 4 wire or half duplex Over 2 wire line. ONLY£85.00 PER PAIR +pp C 1000

.r more information contact our Sales Office.

MATRIX P,SPECIAL BULK PUR HA E of these compact, highspeed matrix printers. Built in Japan for the HazeltineCorporation this unit features quality constructiongiving 100cps bidirectional, full pin addressablegraphics, 6 type fonts, up_ to 95 single sheet ortractor paper handling, RS232 and CENTRONICSParallel interface Many other features BRAND NEWand BOXED. COST £420 Our price Only £199.00

Dry Fit MAINTENANCE FREE by SonnenscheinYuasa.

A300 0719131 5 12v 3Ah NEW £13.95A300 07191312 6v 3Ah NEW £9.95A300 07191202 6-0-6v 1 8Ah TESTED Ex

Equip £5.99

VDU TE r MINALSStandard VDU data entry terminals

at give sway prices!!OUME OVT108. Current product, state of the artterminal with detachable keyboard, 12 Green screen.2 page RAM, TVI 925. Hazeltine. ADMSA emulations,software setup. 25 x 80. Clock. Swivel and tilt base.Printer port, Function keys etc BRAND NEW andBOXED AT ALMOST HALF PRICE Only £425.00AJ510 - EX RENTAL, Z80 controlled, 15 greenscreen 24 a 80 display, graphics, cursor addressing,printer port etc. Very good condition TESTED completewith manual only £225.00ADDS 520 - Dumb terminal, used, 12 b/w screenRS232 interlace and printer port. TESTED.ONLY £125.00. Carriage on terminals £10.00100's of other terminals in stock. CALL for more details.

All prices quoted are for U.K Mainland. paid cash with order in Pounds Sterling PLUS VAT. Minimum order value E2.00.Minimum Credit Card orderE/0.00 Minimum BONA FIDE account orders from Government Depts.. Schools. Universities andestablished companiesE20.00. Where post and packing not indicated please ADD C 1.00 + VAT. Warehouse open Mon -Fri9 30-5.30.Sat 10.30-5 30 We reserve the right to change prices and specifications without notice. Trade. Bulk and Export

LLCL I KUI --111Lil_ _Ci r n ri-C 32 Biggin Way, Upper Norwood, London SE19 3XFTelephone 01-679 4414 Telex 894502 Data 01-679 1888 .


FRS PRINTERS PRINTERS PRINTERSSUPER DEAL? NO - SUPER STEALTHE FABULOUS 25 CPS "TEC STARWRITER"

,/ ///////////

Made to the veryhighest spec the TECSTARWRITERFP1500-25 features avery heavy duty die castchassis and DIABLOtype print mechanismgiving superbregistration and printquality Micro -processorelectronics offer fullDIABLO/OUME command comparability ana turf con ro via CPM WORDSTARETC. Many other features include bi-directional printing, switchable 10 or 12 pitchfull width 381 mm paper handling with up to 163 characters per line. friction feedrollers for single sheet or continuous paper. internal buffer, standard RS232 serialinterface with handshake. Supplied absolutely BRAND NEW with 90 day guaranteeand FREE daisy wheel and dust cover Order NOW or contact sales office for moreinformation Optional extras RS232 data cable £10.00 Tech manual £7.50 tractorFeed £140.00 Spare daisy wheel £3.50 Carriage 8 Ins (UK Mainlandl 110 00

a fraction of its original cost.

NOW ONLY £499 + VAT

DIY PRINTER MECHBrand New surplus of this professional printer chassis gives anoutstanding opportunity for the Student. Hobbyist or Roboticsconstructor to build a printer - plotter - digitiser etc. entirely to theirown specification. The printer mechanism is supplied ready built.aligned and pre tested but WITHOUT electronics. Many featuresinclude all metal chassis, phosphor bronze bearings. 132 characteroptical shaft position encoder. NINE needle head. 2 x two phase 12Vstepper mctors for carriage and paper control. 9.5 Paper platten etcetc. Even a manufacturer's print sample to show the unit's capabilities"Overall dimensions 40 cm x 12 cm x 21 cm.Sold BRAND NEW at a FRACTION of cost ONLY £49.50 + pp £4.50

TELETYPE AS1---33DATA I/O TERMINALS

Industry standard, combined ASCII110 baud printer, keyboard and 9hole paper tape punch and reade-Standard RS232 serial interface.Ideal as cheap hard copy unitor tape prep. for CNC and NCmachines TESTED and in goodcondition. Only f 250.00 floorstand £10.00. Carr & Ins £15.00.

EX NEWSSERVICE PRINTERS

Compact ultra reliable quality built unitmade by the USA EXTEL CorporationOften seen in major Hotels printing up tothe minute News and Financial inform'ation. the unit operates on 5 UNITBAUDOT CODE from a Current 100P,RS232 or TTL serial interface May beconnected to your micro as a low costprinter or via a simple interface and filterto any communications receiver toenable printing of worldwide NEWSTELEX and RTTY servicesSupplied TESTED in SeCo id handcondition complete with DATA, 50 and75 baud xtals and large paper roll.TYPE AE11

50 Column ONLY £49.95Spare paper roll for AE I 1 14.50TYPE AF1 1 R 72 Col

+ Ribbon £65.00TYPE AH11 R 80 Col

ASCII/BAUDOT £185.00Carriage and Insurance £7 50

20,000 FEET OF ELECTRONICAND COMPUTER GOODIES

ENGLAND'S LARGEST SURPLUS STORE - SEEING IS BELIEVING"

DEC CORNER MAO TAPE DRIVESPDP 1140 System comprising of CPU, 124kmemory 8 MMU 15 line RS232 interface.RPO2 40 MB hard disk driveTU10 9 track 800 BPI Mag tape drive. dualtrack system. VT52 VDU. etc. etc Tested andrunning £3,750.00BA11-MB 3,5 Box, PSU. LTC £395.00DH11-AD 16 x RS232 DMAinterface £1,900.00'XVI 1-J4 x EIA interface £350.00DLV11-E Serial. Modem support £190.00DUP11 Synch. Serial data i/o £650.0000200 Dilog - multi RK controller £495.00DI11-E1 8 line RS232 mux board £650.00KDF11 M8I89 PDP 1123PLUS £1,100.00LA30 Printer and Keyboard £80.00LA36 Decwriter EIA or20 mA loop £270.00MS11-JP Unibus 32kb Ram £80.00MS11-LB Unibus 128kb Ram £450.00MS11-LD Unibus 256kb Ram £850.00PDP11/05 Cpu Ram, i/o etc £450.00PDP11/40 Cpu. 124k MMU £1,850.00RT11 ver 3B documentation kit £70.00RK05-J 2.5 Mb disk drives £650.00KL3 JA PDP 8 async i/o £175.00M18E PDP 8 Bootstrap option £75.00VT50 VDU and Keyboard- 20 mA £175.00VT52 VDU and RS232 interface £250.00

Give your VT100 a Birthday"'Brand New VT100 Keyboards

only C85.00

1000's OF EX STOCK spares for PDP8, PDP8APDP11, PD P1134 etc. SAE. for list or CALLsales office for detailsALL TYPES OF COMPUTER EQUIPMENT ANDSPARES WANTED FOR PROMPT CASHPAYMENT.

Many EX STOCK computer tape drives and spares byPERTEC, CIPHER, WANGO, DIGIDATA, KENNEDYetc. Special offer this month on DEI Cartridge tapedrives ONLY £450.00 each.

CALL FOR DETAILS

COMPUTER/SYSTEM CABINET 6 PSUAll in one quality computer cabinet with integralswitched mode PSU. mains filtering. and twin fancooling. Originally made for the famous DEC PDP8computer system costing thousands of pcunds.Made to run 24 hours per day the psu is fullyscreened and will deliver a massive +5v DC at 17 amps. +15v DC at1 amp and -15v DC at 5 amps. The complete unit is fully enclosedwith removable top lid. filtering, trip switch. power and -un ledsmounted on all front panel, rear cable entries. etc etc. Units are ingood but used condition - supplied for 240v operation complete wrhfull circuit and tech. mail. Give your system 'hat professional finishfor only £49.95 + carr 19 wide 16 deep 10.5' high Useable area16 w10.5 h11.5 d.Also available less psu. with fans etc. Internal dim. 19 w. 16 d. 10.5' h.£19.95. Carriage £8.75- _66% DISCOUNT ON COMPONENTS

ELECTRONIC

EOUIPMENT

Due to our massive bulk purchasing programme. which enables us to bring yoc thebest possible bargains. we have thousands of ICs. Transistors. Relays. Caps. PCBs.Sub -assemblies. Switches etc etc surplus to OUR requirements Because we don'thave sufficient Stocks of any one item to include in our ads we are packing all theseitems into the BARGAIN OF A LIFETIME Thousands of components at giveawayprices Guaranteed to be worth at least 3 times what you pay Unbeatable value andperhaps one of the most consistently useful items you will every buy"' Sold byweight

2.5kIs £5.25 + pp £1.25 5 kls £6.90 + £1.8010kIs £11.25 + pp £2.25 20kls £19.50 + pp £4.75

GE TERMIPRINTER

A massive purchase of these desk topprinter terminals enables us to offer youthese quality 30 or 120 cps printersat a SUPER LOW PRICE against theiroriginal cost of over 11000 Unitcomprises of full OWERTY electronic,keyboard and printer meth with printface similar to correspondence qualitytypewriter Variable forms tractor unitenables full width - up to 13 5 120column paper. upper - lower casestandard RS232 serial interface internalvertical and horizontal tab settingsstandard ribbon. adjustable baudrates. quiet operation plus many otherfeatures Supplied complete with manualGuaranteed working GE30 £130.00.GE1200 120 cps £175.00Untested GE30 £65.00 porstand £12.50 Carr 8 Ins i '

SEMICONDUCTOR'GRAB BAGS'

Mixed Semis amazing value -,c,ntentinclude transistors digital linear IC striacs. diodes bridge recs. etc etcAll devices guaranteed brand new fullspec with manufacturer's markings. fullyguaranteed50+ £2.95 100+ £5.15TTL 74 Series A gigantic purchase of anacross the board' range of 74 TTL series

IC s enables us to offer 100+ mixed"mostly TTL" grab bags at a price whichtwo or three chips in the bag wouldnormally cost to buy Fully guaranteed allIC s full spec 100+ £6.90.200+ £12.30, 300+ £19.50

MAIMS FILTERSCURE those unnerving hang ups and dataglitches caused by mains interference withprofessional quality filters SD5A matchbox size up to 1000 watt 240 VLoad ONLY £5.95. L12127 compactcompletely cased unit with 3 pin fittedsocket up to 750 watts ONLY £9.99

EPROM COPIERSThe amazing SOFTY 2 The CompleteToolkit for copying writing modifying andlisting EPROMS of the 2516. 2716.2532. 2732 range Many other functionsinclude integral keyboard cassette inter-face serial and parallel i o UHF modulatorZIF socket etcONLY £195.00 + pp 12 50"GANG OF EIGHT" intelligent Z80controlled 8 gang programmer for ALLsingle 5v rail EPROMS up to 27128 Willcopy 8 27128 in ONLY 3 MINUTES InternalLCD display and checking routines forIDIOT PROOF operation Only £395.00 +pp 13 00"GANG OF EIGHT PLUS" Same spec asabove but with additional RS232 serialinterface for down line loading data fromcomputer etc ONLY £445.00 + pp £3.00

Data sheets on request

COOLING FANSMow, Your not pans COOL dnit RELIABLE o our tamp 5COLING FANS ETRI 126LF21 240, 5 Om,. eduturnent tan1,o, BO 80 38rnm C9 95 ETRI 99XU01240. Sltent,neDtro 92 92 25(11T1 edu,pmem gran NEW f 9 95GOULD JB 3AR Dim 3 3 2 5 compact vet. q.Jetunntng 240v opetatton NEW LB 95 MUFFIN CENTAUR

BOXER standard 120 120 38mtn tans Otclet 110, 08240v 3 of 5 blade. NEW at (10 50 or tested EX EQUIPMENTCS 50 Lour Voltage DC Fans BUHLER 69 11 22 8 16, DC1,CIO mtnmature tevets,Ole Uses 13,,,,PSS se", mut.,almost tonntng guaranteed 10 000 n. Itte Measure,oniv 62 62 22n,n, Current ost C3500 OUR PRICEONLY E13 95 t omplete vvan data i 20 120 38nwnDC tans, PANSONIC FR 12C1214 12, DC S Dude (1800PAPST 4124X 20 :P. r'' ,! i,. f 18 00

1000's of other EX STOCK items including POWER SUPPLIES, RACKS, RELAYS, TRANSFORMERS, TESTEQUIPMENT, CABLE, CONNECTORS, HARDWARE, MODEMS, TELEPHONES, VARIACS, VDU'S,PRINTERS. POWER SUPPLIES, OPTICS, KEYBOARDS etc. etc. Give us a call for your spare part -',requirements. Stock changes almost daily.Don't forget, ALL TYPES and QUANTITIES of electronic surplus purchased for CASH



PioneersW. A. ATHERTON

7. Alexander Graham Bell(1847-1922):

speech shaped current

What do the following items have incommon: the National GeographicSociety, the American magazine

Science, aircraft ailerons, and sheep withfour nipples? No. it's not Trivial Pursuit. Allwere steered into existence by the same man,the inventor of the telephone.

To most people the telephone is one of thegreatest inventions of all time. Yet oneAmerican newspaper reporter wrote "It is aninteresting toy . . . but it can never he of anypractical value."

That reporter was not alone in dismissingthe new invention. A British official thoughtit might prosper in the colonies hut not inBritain since "we have an abundance ofmessenger boys". And the great WesternUnion Telegraph company rejected an offerto buy the patent. "Bell's profession is that ofa voice teacher." they observed. "Yet heclaims to have discovered an instrument ofgreat practical value in communicationwhich has been overlooked by thousands ofworkers who have spent years in the field."

The patent Western Union turned downwas one of the most lucrative ever issued. forthe commercial success of the telephone wasas immediate as it was dramatic. AlthoughBell at first gave lectures and demonstra-tions to raise much -needed cash (reservedseats cost 50 cents and the first profit was$149) the success of the telephone made himand his assistant, Thomas Watson. financial-ly secure by 1881. The telephone was by thena mere five years old.

Western Union did, however, get onething right in their assessment of Bell: hewas indeed a teacher of the deaf.

Born in Edinburgh on March 3. 1847. hewas christened Alexander. On his eleventhbirthday he decided he would like a secondChristian name and chose Graham. He andhis two brothers inherited a family traditionof teaching elocution. His grandfather hadpractised in London and his father was theinventor of a phonetic alphabet called VisibleSpeech. Both Bell's mother and wife weredeaf. Helping deaf people learn to speakbecame his main career.

Bell received his early education from hismother and he became an accomplishedpianist. At ten years of age he started school.

By the time he entered University College.London at 20, he had taught elocution atElgin. Edinburgh and Bath.

At university he studied anatomy andbiology. But before that, in a letter to hisfather. he had written up his first scientificresearch, on the resonant pitches of mouthcavities. As a result of this he was introducedto the work of Helmholtz and gained his firstknowledge of electricity.

His brothers died early from tuberculosis.Partly fearing for the health of their remain-ing son, the family quit Britain for thehealthierclimateof Canada on August 1.1870.

In Quebec. Bell taught his father's VisibleSpeech to deaf pupils and began to teachteachers of the deaf. In 1873 he wasappointed professor of vocal physiology atBoston University. Nine years later he be-came a US citizen, and very proud of the facthe was too.

MAKING SOUND VISIBLE

Work with the deaf turned Bell's intellect toall things related to the human voice. Insearching for teaching aids he came acrossthe phonautograph. a device with a conicalmouthpiece and a stretched membrane

which vibrated in response to the voice. Themechanical vibrations were conveyed to astylus which traced the wave pattern of thevoice on to a moving piece of glass blackenedwith soot.

These and other attempts to make a visualrecord of a human voice for use as a teachingaid for the deaf were crucial to the inventionof the telephone. The step from a mechanicalrecord of voice waves on blackened glass toelectrical waves in a wire was the mark ofgenius. But it did not come in a flash.

For several years Bell had been activelyinterested in telegraphy and a parallel prob-lem with which he now wrestled was how touse an intermittent electrical current totransmit musical tones via the telegraph.This he thought possible if the vibrations ofthe air could he somehow reproduced in anelectrical current.

In the summer of 1874 he visited hisfather's home in Brantford, Canada. takingwith him a human ear provided by theHarvard Medical School. The idea was to usethe ear and the small hones of the ear tomake an improved phonautograph: a pieceof hay acted as the stylus. The human -earphonautograph worked!

If the relatively massive hones of the ear


This instrument was used to transmit the first speech sounds electrically in 1875. Theparchment diaphragm is attached to a magnetized metallic reed. Piture from AT&T.

could he vibrated. thought Bell. why not asmall piece of steel? The basic concept of thetelephone now crystallized. though its prac-tical achievement was still far away. When apractical realization came we can he thank-ful that the mouthpiece did not need ahuman ear cut from a corpse.

Whilst continuing his work with the deafin Boston. Bell had for some time beenworking on ideas for a multiple telegraph.one which would enable simultaneous sig-nalling of many messages to take place alonga single line. By this time he had met a youngmachinist. Thomas A. Watson. and towardsthe end of 1874 they worked together atBell's idea for multiple telegraphy. In thatsame year Bell explained his telephone ideato the aged Joseph Henry. seeking his adviceas to whether to publish the idea so thatothers could work at it or to finish it himself.Henry told Bell to finish the work himself.When Bell confessed that he did not have theelectrical knowledge needed Henry's advicewas blunt: "Cet it!"

Bell meantime had obtained financialhackers: not for the telephone. but for themultiple telegraph, for which his hackershad greater hopes. (When the telephonebecame a success Bell himself insisted that ithe part of the agreement.)

A LITTLE ACCIDENT

With his experience of the phonautographand his mental concept of the telephone, alittle accident with the multiple telegraphequipment showed Bell how to achieve hisdream of electrical speech.

The multiple (or harmonic) telegraph wasto work as follows. At the transmitter andreceiver there were tuned vibrating reeds. Areed at the transmitter tuned to a frequencyft could. according to the theory. send apulsed signal which would only he detectedby a reed also tuned to fi at the receiver.

Several reeds tuned at different frequencies(f1. f,. f3. etc) should enable several pulsedsignals to he transmitted simultaneously.

On June 2. 1875. in the middle of a bakinghot afternoon. Watson and Bell were retun-ing the reeds when one of Watson's trans-mitter reeds stuck. The adjustment screwhad been screwed too far. To restart Watsonplucked it and Bell, at the receiver, gave aloud shout.

Held too hard, the reed had failed tointerrupt the current and had produced acontinuous sine wave instead. Bell recog-nised the answer to his dreams. The rest ofthe afternoon and evening were spent re-peating and repeating the discovery.

By the time they parted Bell had sketchedout a diagram of the first telephone andbegged Watson to try to build it ready for thenext evening. "And. as I studies the sketchon my way home to Salem on the midnighttrain." Watson recalled. "I felt sure I could doso." He did. The next evening the first faintsounds (not speech) were transmitted andreceived. As yet unintelligible they provedBell's basic idea.

During the ensuing months. work on themultiple telegraph took enforced priorityover the telephone. along with ill health.personal crisis. and teaching duties. AnAmerican patent covering the telephone wasallowed on Bell's 29th birthday. March 3.1876. It was actually issued four days later.

On the evening of March 10. intelligiblespeech was achieved using a 'liquid' trans-mitter and a tuned -reed receiver. In the newtransmitter, designed by Bell and built byWatson. a metal wire attached to a dia-phragm was dipped into acidulated water.The water and wire were part of the electricalcircuit. As sound waves vibrated the di-aphragm. the wire moved up and down inthe liquid and so varied the resistance of thecircuit. The telephone had arrived.

New transmitters and receivers followed.

An early British instrument, of about 1890:a wall telephone of the National TelephoneCompany. Picture from British Telecom.

some using liquids and some employing therelative movements of magnetized coils andpieces of iron. These were demonstrated atthe Centennial Exhibition in Philadelphia onJune 25. 1876 (the day of Custer's last stand)and impressed all who saw them. LordKelvin. who was one of the technical judges.ran the 100 -yard length of the gallery fromthe receiver to the transmitter to congratu-late the inventor.

COMMERCIAL SUCCESS

Watson. after some persuasion. resigned hiswell -paid full-time job to take up full-timework on the telephone. He received a tenthshare of the patent. In November. using yetanother new design. successful tests wereconducted between Boston and North Con-way in New Hampshire using a railwaytelegraph wire. a distance of over 100 miles.

A company was formed in July 1877 two orthree months after the first regular tele-phone lines opened in Boston. Other Bellcomnanies followed swiftly for variousreasons. and a reorganization in 1880 cre-ated the American Bell Telephone Company.

Western Union meanwhile had set up incompetition after the principle of the tele-


phone had become known. Bell sued forinfringement of his patents and won. TheBell patents were repeatedly defended in thecourts, on about 600 cases, before theSupreme Court eventually upheld all Bell'sclaims.

Bell meanwhile had married Mabel Hub-bard. one of his private pupils and thedaughter of one of his financial backers, onJuly 11. 1877. The marriage was long andhappy despite the loss of two of their fourchildren at birth. In August they sailed toEurope to promote the telephone, leavingWatson in charge for over a year. At the timeof the wedding a couple of hundred tele-phones were in operation.

By 1881 both Bell and Watson had movedon to other interests.

Bell continued his absorbing interest inteaching the deaf to speak well. His interestin hereditary deafness led him to studies oflongevity and breeding. In 1909. after 20years' selective breeding, he had a flock ofsheep with four or more milk -producingnipples rather than the usual two! Thereinlies a tale in itself.

In 1880 France awarded Bell the VoltaPrize of 50 000 francs. This he used toestablish the Volta Laboratory Association inWashington to work with the deaf. Two yearslater he conceived the idea for the journalScience which began publishing in 1883. Inits first eight years Bell and his father-in-lawsubsidized the journal to the tune of around$100 000.

Bell also helped organize and finance theNational Geographic Society and was itspresident for several years. and he gave$5000 to establish the Smithsonian Astro-physical Laboratory.

For the last 25 years or so of his life one ofhis main interests was aviation. With a gift of$50 000, he founded the Aerial ExperimentAssociation under whose auspices some ofthe earliest flights took place in 1908. Belland the Association held the patent for thedesign of ailerons for wings and rudders.

He also invented a tetrahedral construc-tional technique known as space frame, triedto introduce the Montessori educationalmethod to America. and developed an in-terest in designing hydrofoil boats. One ofhis hydrofoils gained the world water speedrecord in 1919 at 70.86 miles per hour.

Amongst the honours Bell received wasthe freedom of Edinburgh (his birthplace).the opening of the first trans -continentaltelephone link between New York and SanFranscisco in 1915, and the naming of anisland after him.

After his death in 1922. at the age of 75. hewas buried in a rock tomb on top of amountain. Every telephone in North Amer-ica was silent for one minute during hisfuneral.

Next in this series of pioneers of electricalcommunication will be Oliver Heaviside.

Tony Atherton works at the IndependentBroadcasting Authority's engineering train-ing college in Devon. His book. From Com-pass to Computer. A History of Electrical andElectronics Engineering, was published byMacmillan in 1984.

68000 -familyPascal machineIf you need to decide which computer language to use foryournext industrial control system, one of the new breed of Pascal

compilers may be ideal.

W.P. STANLEY

pascal was designed as an easy -to -learnlanguage to teach students how towrite programs, which humble begin-

ning it shares with Basic but unlike thatlanguage, Pascal enforces the concept ofstructured programming. To someone whohas used Basic, Pascal may appear to bepedantic, it lacks a 'goto' statement forinstance, but its strength is that it forces theprogrammers to understand the true natureof the task before starting to write a pro-gram. This means that the program is

produced in the correct construction, if notin detail, the first time round as opposed to apoorly concieved core modified by layers of'goto' statements and extra modifications toget it to work. Even if the time taken to writein both forms is the same, the real costadvantage of Pascal is that the resultingprogram is self -documenting to a largeextent, which leads to easier and fastermaintenance.

One of the strengths of Pascal is itscomprehensive selection of data types avail-able to the programmer, which now encom-pass boolean, character (byte), enumeratedtype, integer, longinteger, hex, longhex,real, string, array, record, devices and files,and pointers. The string functions, so long aweak point in Pascal, have now been en-hanced to give similar performance to thosein Basic, which has always enjoyed powerfulstring operators.

Pascal has been limited by some of thesame problems as Bask in that it was onlyavailable in an interpretive form or withintermediate code output which producedslow executing programs. This tended topreclude control by the programmer as towhere variables were held: the compiler orinterpreter allocated space in the memory,usually via the stack, or optionally on areverse stack, the 'heap'. without any bear-ing on the wishes of the programmer. Forindustrial control, or for any applicationwhich wants to poke its nose outside theconfines of the operating system, it is essen-tial to be able to access absolute addresses inthe memory map to talk to i/o ports. This isnow possible in Pascal because the user can

specify how the variables are held; on thestack (by default), at an extended (absolute)address, program counter relative, definedin another module or, on 16bit processors,in a c.p.u. register.

A requirement for most programs is theability to perform simple operations on allrelevant classes of data without large proces-ing overheads; things like OR. EOR. AND. NANOand shift. This limitation is overcome in thelatest generation of Pascal compilers, whichcan produce compact 'romable' position -independent object code that is frugal onmemory and has a runtime library overheadproportional to the function used. To givefigures for one particular compiler, theOmegasoft 68000 Pascal compiler, typicalruntime overhead is between 1 and 3Kbytes,with a minimum of about 50 bytes and amaximum of 10K using every function anddata type: the compiler efficiency is about0.4 that of hand -coded assembler but theexecution speed is fast. This compares wellagainst a C compiler running on the sameoperating system; the code efficiency isabout the same and the Pascal programsusually execute faster. This is not intendedto show that Pascal compilers are 'better'than C compilers, simply that they arecomparable and that C code is not automati-cally the optimum solution.

Another development, which has becomemore common in the later compilers, is tosurround the compiler with a suite of utili-ties that make the task of converting theprogram into debugged object code mucheasier. In the example of Omegasoft Pascal,this takes the form of a easy -to -use linkagecreator which asks the user a series ofquestions about the physical properties ofthe hardware and produces a small assemb-ler program as a result. This sets all therelevant stack pointers for the main Pascalprogram and also produces a procedural filewhich will assemble and link all the neededmodules.

A type of utility that has become popular isthe interactive debugger, which will allowthe programmer to debug software at Pascalline level. to be able to breakpoint to a line


68000 -FAMILY PASCALENVIRONMENT UP -DATE

Can now compile programs from inside theeditor so that syntax checking of a new piece ofcode is now very quick. Errors found by thecompiler in this mode are passed back to theeditor on a stack, and can be popped off thestack by an editor command to quickly movefrom error to error. Compiler now supports longreal types in theIEEE 64 -bit format and can support the 68881floating point coprocessor as a peripheral. A 'Pascal shell' provides a complete Pascalprogramming environment for each project Thiskeeps track of all the related files in a suite ofprograms so that when changes are made to onefile it it easy to recompile and link all the modulesback together with just a few keystrokes. It alsoallows considerable control over the recompila-tion: you can specify to recompile all filesmodified after a certain date and time, or afterthe date on a particular file. Only the files relatedto the task are kept inside the shell environmentso that the rest of the operating system 'clutter' isnot obscuring the work. All the Omegasoft utili-ties are catered for from inside the shell. It ispossible to edit a set of files. then tell the shell torecompile and load the debugger. leaving theuser ready to start debugging or recompile,assemble and link and produce 'romable' codefiles. An optimized 68020 version of the compilerwill support f.p.u. (68881 and 68882) directly onthe coprocessor interface with in -line code, andshould be available in July or August Source code of the pascal shell, linkagecreator. screen editor and runtime library areincluded for reference.

number, display or change variables byname, trace by line or by procedure. Themore sophisticated debuggers, usuallyfound on 16 or 32 -bit processor versions,will allow assembler modules to be added fordebug along with other Pascal modules, andpermit macro definitions of the debuggercommands. They may even have anassembler -level debug inside which willallow debug and disassembly of assember orPascal programs. A software tool with thiskind of capability is quite a large program inits own right, and a fully-fledged one maytake over 100Kbytes of memory space andassumes that the industrial i/o hardware is inits own memory map. As it takes so muchmemory to support all these features, thiskind of debugging is only found on the larger16/32bit processors and although eight -bitversions are available, the powerful featureshave been trimmed down to allow them to fitinto a 64Kbyte address space.

To give another example, this time Ome-gasoft's 6809 Pascal compiler, where thedebugger uses overlays to maximize the sizeof program it can debug; has no assemblerlevel phase and cannot support macros,though it can single-step, set breakpoints.examine and change variables. It takes about30Kbytes of memory which, when added tothe operating system leaves about 15 to20Kbytes for the program to be debugged.should allow room for between 100 and 400lines of Pascal, depending on the functionsbeing used. Many applications will fit intothis space, but if not then it is possible towrite larger programs as a series of modules.and debug the modules separately beforejoining them all together to produce thefinal object program.

For 16/32 bit processors the overhead of100K for the debugger in a developmentenvironment is not a problem as memory forthese systems is now relatively cheap. Ifdevelopment is done on a modular hardwaresystem such as VME, this may not be toomuch of a problem as the necessary func-

Inc udes

Rscatshell

edttor

LOaGaDiE

Object mod._

t

User data

and results

First introduced to the 6809 market in 1980, Omegasoft Pascal has been expanded andrefined, with major extension to the ISO level 0 standard that allow its use for industrialcontrol and other real-time applications. It is newly available from Certified SoftwareCorporation of California (RCS Microsystems in the UK) to run under OS -9, P -DOS,Versados and CP/M-86K operating systems.

tions can be plugged into the target systemso that in effect it is a development systemwith large amounts of ram and mass storage.After the debugging is complete the excessitems can be removed from the system. If thetarget system is a limited -function systemthat has been designed for a specific purposewithout room to accommodate the hostdebugger, a different approach is needed.and this is provided by a target debugger.

This technique was first used by DigitalEquipment Corp. for their 'Micropower Pas-cal' and has subsequently been adopted byother vendors. It involves writing a smallprogram, usually in assembler, to copy datafrom the target serial port to and from ramon the target system. The bulk of thedebugger now resides in the users host ordevelopment system, which will have massstorage and plenty of ram. and the programto be debugged is passed to the target via theserial port. When excecuted, this target.debug affords the user the same power as thehost debugger, but only requires a small

overhead in the target memory.Pascal has become an excellent tool for

writing software in the industrial controlenvironment. The standard ISO core com-piler with its large selection of data types andextensive intrinsic library functions hasbeen extended to permit easy access tohardware and to overcome some of itsprevious limitations. The result is that pro-grams can be written in Pascal. whichproduces clear and concise listing docu-mentation. that can be just as efficient andfast as any other compiler. Added to that arethe benefits of interactive debugging on ahost or target system and the extra utilitiesfor making stand-alone 'prommable' codeeasily. Could this he the language thatreaches parts of your control system thatother languages cannot reach?

William Stanley is Omegasoft product man-ager with RCS Microsystems of HamptonHill. Middx. tel. 01-9792204.


IMAGE -10HIGH PERFORMANCE SINGLE BOARD GRAPHICS COMPUTER

High performance? they all say that.Ah yes, but. . . .

Image -10 has three 16 bit processors workingconcurrently for dazzling speedandImage -10 has a resolution of 768 by576 pixels for intricate detailandImage -10 has 256 on -screen colours givingphotographic quality.In fact Image -10 has all of therefinements asked of graphics intensiveapplications. Like hardware windows,hardware drawing, hardware zoom and pan,hardware character generation and hardwareblock moves. The only thing the cpu has to dois to run your applications.

Board Price £1295Image -10 includes:

* 68010 cpu * 82786 gdc* Floppy disc controller* Dual RS232 * Centronics

* Battery backed clock* 512K dram * 64K sram* Winchester disc controller

* Mouse * transputer ports* Stereo sound generator* 256K eprom

SOFTWAREDEVELOPMENT

SYSTEMSVersatile, low cost, developmentsystems based on Micro Concepts'single board computer, Microbox 3.A choice of powerful disc operatingsystems is available including Os -9/68K, TRIPOS, and CP/M-68K

Features include:68000 microprocessor, 8MHz clock.512K dynamic ram. 64K static ram.128K epromOn -board graphics controller offers:80 column, 24 row, 16 colour text.640 by 480, 4 colour graphics.320 by 480, 16 colour graphics.Floppy disc controller.Winchester disc controller.Dual serial RS232 ports.Centronics printer port.Up to 48 lines of parallel input/output.Battery backed clock/calendar.I/O expansion capability.Double eurocard board format.

Hardware prices:Fully built and tested Microbox 3 singleboard computer £650System with dual 1M byte floppy discdrives £1195System with 20M byte Winchester andsingle floppy drive £1895

UNIVERSALCROSS ASSEMBLERS

for allMSDOS OS -9 FLEX

computers

Supports the following devices1802 809 80496502 8022 80806803 8039 87516808 80C48 63038021 8051 680280C35 8749 68HC058048 68000 80208050 6301 80358748 6801 8040Z80 6805 80C491805 68HC11 80856800 8031 Z86804 80C39

Extensive directives supportmodular, conditional andstructured program-ming. Powerful Macro Pre-processor, xref generator andoutput conversion utilitiesprovided.

COMPLETE SUITE £295INCLUDES FULL SOURCE CODESNOT 68000)

MICROPROCESSORCONTROLLED

EPROM EEPROM andSINGLE CHIP MICRO

PROGRAMMERPrograms the following devices:2508 2516 25322564 27(C)16 27(C)322732A 27(C)64 2764A27(C)128 27128A 27(C)25657(C)256 27(C)512 275132758 27011 2816A2817A 2864A 2825648Z02 52813 52132352833 68732 6876468766 8741 87428744 8748 87498748H 8749H 87518755 9761 CY7C282CY7C292 DS1225AT -ROM PC -ROM XT -ROM

No Personality Modules required.Controlled via RS232 interface.Accepts Intel, Motorola, Ascii-hexand binary data. Ultra -fast, fast andstandard programming modes.Low and high byte programmingsupported.Completely self contained butuncased. Price £295

All prices shown exclusive of VAT and carriage

Micro) Concepts 2 St. Stephens Road, Cheltenham, Gloucestershire GL51 5AATelephone (0242) 510525



Video frame storeFast look -up table enables the unit to manipulate moving images

in real time for flicker -free special effects.

The frame store is a powerful tool forimage capture, but in its basic form ithas no facilities for real-time image

processing. Manipulation of images musttherefore be done entirely by the - hostcomputer.

The look -up table is a significant enhance-ment because it enables the real-time man-ipulation of pixel grey -levels to be achievedeither by selecting pre-programmed (rom-based) tables or by down -loading computergenerated tables from the host c.p.u. into anon -board high speed ram. These ram -basedtables can be updated during the fieldblanking interval on a frame -by -framebasis.

Look -up tables can be devised forcontrast -stretching (linear or non-linear),histogram equalization, image negation,clipping, noise magnification etc. and theeffect of these operations can be observed onlive as well as frozen images.

The look -up table is constructed on asingle p.c.b. designed to stack with the restof the frame store boards. Installation isextremely simple, involving ribbon cablejumpering to the other boards without any ,

modifications (other than to add appropriateconnectors).

Two memory sockets are provided, one fora high-speed ram chip (typically 2K x 8,6Ons) and one for a high-speed prom (typi-cally 2K x 8, 6Ons). Both sockets can accom-modate slower ram or eprom chips and150ns devices are adequate for the 256 x256

'Earlier articles in this series appeared in Electronics &Wireless World from November 1986 to March 1987. Acorrection to a drawing in the March issue was given thefollowing month at the foot of page 385.

D. E. A. CLARKE

xel datainput

Clock

OE

Latch

CK

Translated pixeldata output

`*- 8

Page select =MI5

Clear

CIR

Address CKcounter

AS -12

Data

tit I,Jontr.:1

CE

t I 3

c.p.0 (control)

8 lines

RIffer OE

Address Ao_7or WR

Cs

Ram

A8-12Data

8

Buffer

Bypassbuffer OE

11 8

c.p.u.(write data)

Fig.l. The look -up table allows pixel grey -levels to be manipulated in real time. Look -updata can be in rom, or can be downloaded into ram from the host computer.


.5

100k 100k

2 11

30 U0

16

Hostdata

IC 401

74HCT 24 4

5

14

_4_ -I%4 All

(I3) 2k2 13 7--4-I a

12

Outputdata (151

D0-7

19

00

7

28 27 26

100n

11.

(Rom)

Do

VSS A8

IC 404TMM20180-45 etc

(Ram) Alpor

82S191 etc WR /An(Rom)

1C405

07

A0

WR

CE/CE

CS

A7 DE

3 22

25

24

21

23 (Rom)

2

23(RamlL3

27(Ram) 1

07

12

IC 403

74 LS 244

13

Do

9

07

08

14 15

Input 7 IC402 6

data 17 74F 374 16

(11) 4 5

18 19

CK2

D7

CKi

Pixel b Licontrol -`-'2 C1(2

(I4) -02

21L6

3_ 4

16

18

3

12

9

14

07

10

2k2

5V

All 4k7

100k

Pageselect

(options)

ROM/RAM"

12k2WRI> 2C)-

L2 WR

100k

IC40874HC104

2

19 1

4 3

15 4

1C406

74 LS244

2 5

17 6-o-8 11

11 10

6 9

13 8

A CKA

B CLR

0

D 741_5393

A 1C407

B CLR

0

0 CKB

13

74HC TOO

Fig 2 All rnmnnncinte fit nn a einala n r h which ran hp iiimnararl to the. nthar haartie A ennrrn of rnm

100k

SLCT

`>2k2Host

control(12)

to ic tritons, eile

configured frame store which clocks atabout 5.8MHz.

The p.c.b. is configurable for several typesof rom and ram devices in 24/28 -pin and300/600 mil packages.

SYSTEM CONFIGURATION

The look -up table is shown in block diagramform in Fig.!. The board is designed to beinserted between the sample bus and thedigital -to -analogue converter on the analo-gue board as shown in Fig.4 (upper). Bothlive and frozen image pixels are then proces-sed in the same way but the image data in theframe store memory always contains truedata. The colour palette can be located onthe look -up table input bus or on thetranslated pixel output bus.

Two other configurations are also pos-sible:1. The look -up table can be positionedbetween the analogue -to -digital converterand the image memory as shown in Fig.4(lower) and the image data in ram will thenbe translated prior to storage as well asdisplay.2. Both configurations can be implementedsimultaneously using two look -up table

boards to achieve both image write datatranslation and image read data translationat the same time.

The latter configuration cannot usually bejustified for normal applications.

CIRCUIT OPERATION

The complete circuit is shown in Fig.2.Incoming eight -bit pixel data is retimed byIC402 which latches the data on the rising

edge of the sample clock: a complete clockcycle is then available for memory accessbecause output data is latched by the d.a.c.and colour palette boards on the next risingedge of CLOCK. This extra delay of one pixelcauses the displayed image to be displaced tothe right. and shifts into view a hidden pixelat the left of the picture while 3Ianking thepixel on the right. This is of no consequencefor displayed images since there are severalperfectly valid hidden pixels. but image

ROM/ IVAN

DATA

WR

I 1f

Fig.3. Sequence for downloading data to the look -up table's on -board ram.


manipulation software should be designed totake the displacement into account.

The latched pixel data directly addressesthe on -board rom or ram and the resultantoutput data becomes the new pixel value. Itfollows that 256 grey levels can be translatedinto 256 alternative values depending uponthe contents of the addressed table.

Using 8K x 8 memory devices gives thecapability for up to 32 tables selectable byoptional external switches.

Ram or rom-based tables are selected bythe host control signal ROM/M which whenhigh (or open -circuit) selects the rom or, ifa rom is not fitted, the bypass buffer IC4(0.The bypass mechanism enables the framestore to be operated without the host'shaving to initialize the on -board ram.Various control signals are derived by IC408and IC40,; these are 74HCT series devices asis the host data buffer IC401 for ease ofinterfacing and good noise immunity.

The host gains access by assertingwhich enables the address counter IC4,G.enables buffers IC406, IC401, disables latchIC402, disables buffer IC403 and three -statesthe ram/rom output buffers. The ram isenabled by taking liorwW4 low and data written by pulsing wri low. The address counteris incremented on the rising edge of vTrwhich provides for very fast table updating.

Taking s= -r high enables pixel translationby enabling the latch IC402 and either therom or ram depending upon the controlsignal ROM/12/4 and disabling buffers1C401,406. Link 1 normally selects cr8i; Link 2allows two look -up table boards to beindividually programmed by pulsing theappropriate wR line.

Link 3 will normally be in position 1 for2K x 8 ram devices when pin 23 is n. Link 4allows the use of rom devices when thepolarity of pin 20 changes. Link 5 should bein position 2 when a rom is not fitted; thisenables the bypass buffer IC403 (which canotherwise be omitted).

When the look -up table is positionedbetween the sample bus and the a -to -d onthe analogue board, it must be disabledduring c.p.u. frame memory update; thesignal Er is used for this purpose and isselected by Link 6 in position 2.

PROGRAMMING

The sequence for programming the look -uptable ram is shown in Fig.3. The line istaken low, liomiwN is taken low and data isoutput to IC401; vTii is then pulsed low andthe cycle repeated. Finally, si.r is takenhigh to enable the look -up table.

This example program generates a tablefor negative displayed images:

PROGRAM NEGATIVE;

BEGIN;OUTPUT( SLCT ) := 0;OUTPUT( ROM/RAM ) := 0;FOR COUNT := 0 TO 255 DO

BEGIN;OUTPUT( DATAPORT ) :

OUTPUT( WR ) := 0;OUTPUT( WR) :=1;

END;OUTPUT( SLCT ) :=1;

END.

cpu control /data

Controlboard

Pixel control

Paletteboard

Lookup tableboard

Out

8

d- to -a cony

Memory n Analogueboard t board

o -to -d cory

ontrolboard

P,xel contro'

Memoryboard

cpu control/datn

Lookup tableboard

Out

Into -a cone

Analogue8 board

8 o -to -d cony

Fig.4. Two contrasting arrangements of the look -up table: above, the frame store memoryalways contains true data; below, image data is translated prior to storage.

Table 1: Link programming All are two way change -overlinks

Link Position 1 Position 2

1 normal2 personality (see text)3 TMM2108 ram4 active low5 rom fitted

6 board location(see text)

6264 ramactive high rom selectauto -bypass in rom-lesssystem

INSTALLATION

Note when installing the look -up table thatthere is an option for separate data buses forthe d.a.c. and a.d.c. on the analogue board,as shown in Fig.11 of the December 1986article. The links which connect these busestogether should be left open -circuit and anadditional connector installed so that sepa-rate connectors are available for d.a.c. anda.d.c. data. There is provision for this on thep.c.bs available for this project.

The ribbon cable carrying pixel databetween the memory board, colour palette(if fitted) and the converter board shouldnow be connected as follows:

(SELECT HOST ACCESS MODE)(SELECT RAM)

(UPDATE 256 LOCATIONS)

= NOT COUNT; (OUTPUT NOT COUNT AS DATA)(STROBE RAM AND INCREMENT ADDRESS)

(ENABLE PIXEL TRANSLATION)

memory--Took-upAn additional jumper cable should beassembled and used to connect

look -up (output).palette--41.a.c.

Finally, the look -up table p.c.b. must beconnected (in parallel with the other boards)to the pixel control bus and the host inter-face buses by clamping additional connec-tors to the appropriate ribbon cables.

FEATURES OF THE LOOK -UP TABLE

Eight -bit picture element data input Eight -bit translated data output 256 entries per table Throughput to 15MHz Up to 32 rom-based tables Up to 32 ram -based tables Auto bypass User -configurable hardware options Simple installation

With the addition of a clock generator, aneight -bit counter to simulate incoming pclsand a d.a.c. at the output this design couldalso be used as a programmable arbitrarywaveform generator with time resolutiondown to 65ns. For a suggested design whichavoids the need to modify the p.c.b. send astamped, self-addressed envelope to theeditorial office. Mark your covering envelope 'Video frame store'.

P.c.bs and components are available fromIpswich Electronics Ltd, Hadleigh Road In-dustrial Estate, Ipswich IP2 OHB, tel. 0473-216056; semiconductor devices from Tech-nomatic Ltd, 17 Burnley Road, LondonNWIO lED, tel. 01-723 1177.


101

PHONE P. M. COMPONENTS LTD TELEX0474 60521 SELECTRON HOUSE, SPRINGHEAD ENTERPRISE PARK 966371

4 LINES SPRINGHEAD RD, GRAVESEND, KENT DA11 8HD TOS-PM

INTEGRATED CIRCUITS

451.-I 2.50AN71.00 2.50AN.510P 2.90

215414,1/. 150AN' mo 350

350335

A 1352E 1 7503086 046A 073C 1.50

t 366W 3.50HA1377 3.50HA 156W 1.50HA i34 2951181398 2.751181551 2.951A1230 1.95LA403, P 196LA4102 2.95151140 2.95154400 415LA4420 I 95144477 2.50144430 2.50LA4401 3.95LC7120 3.25LC7130 310107131 5.50L10324N 0.45LM.160604 1.751193831 2951M390019 350M5,5131 2.3054515151 2.9519515211 1.501983712 2.00MC 1307P 1.00M( .I 11,:1: I50

Mt. 13.- 1 7061C13:49P 1.20MC1351P 1.50MC1352P 100MC1357 2.35MC1358 1.58MC1495 300MC1496 1.25MC145106p7

795MC 1 723 050MC3357 2 75Ml 7318 I 75MSM5807 6.75P1.1028 5 75SAA5008 350SAA1025 725SAS560S I 7558S5700 1 75SA5580 2 0551.9170 75051.1310 1.6051.1327 1 1051 13270 110SN76003N 3955N -6023N 3.95y'smON 089y I SN 1 25

P. 2 95

65265

15

7 957 95

I I 95II 95

STK085 6.95STK433 5.95STK435 7.95STK437 7.95STK439 7.95516461 11.50STK463 11.50TA7061AP 3.96TA7108P 1.50TA7120P 1.66TA7130P 1.50TA7176AP 2.06TA7203 2.56

A7.504P 2.15'735AP 1.16

1.90278 4.25

OOP 1.90, 13AP 2.95

:2IP 2.2S146P 2.50

3.955 -611AP 2.96

'083105 3.50TAA320A 3.501883505 3.50TAA570 1.95TAA66113 1.95TBA700 1.7011,120AS BC

5 -13 T U 1.00(95 1.50

. 1551251502.50

TBA520 1.101085200 1.107138530 1.1071385300 1.10188540 1.251085400 1.36

71385500 1 95TBA560C 1.45TBA460C0 1.457138570 1.00TBA651R 2.507E157204 2.45TB87500 2.6.57135800 019TBA810AS 1.65TBABIOP 1.65TBA820M 075TB/48200 1A5TBA1390 2.50TEI5920 165TBA950 24 23518A990 1.49TCA270 1.50TCA27050 110TCA650 150TCA940 1.65TCEP100 2.50104440 3.50TDA1001 2.9510410028 2.95T0800064 2.501041035 2107081037 1.9510510748 2.50TDA1.70 195TDA1190 215TDA. 2700 050TDA1327 1.70TDA2002 I 95TDA2003 1.95TDA2004 2.957082005 2957082006 195TDA2020 2.951042030 2101082523 2.95TDA2524 1951082530 1.95T082532 1.95

T082540 115TDA25454 2.15TDA2451 2151082560 2.15TDA25714 4.507082581 2.95TDA2593 2.951082600 1150TDA2610 3.507082611A 1.951052640 35010826804 2 751042690 2 457083310 295TDA3560 1501084600 2.50uPC56634 2.9508057502 2 75UPC102534 1 95uPC10281.4 1.95UPC1032H I SOUPC , ,5613 2 75080115811 0.75UPC1157C2 1 95UPC1181H 1 25UPC1182H 2.95UPC1185H 3 95UPC11911/ 1.50UPC1350C 2.95UPC1353C 2.45UPC1365C 3.95UPC2002H 195555 036556 060723 050741 0 35747 050748 0 357805 0 6571308 0607815 065

SEMICONDUCTORS

AA11. 025AC115 020AC.126 045AC127 020AC 126 020AC1286 032AC.4. 028A(.1:.079

022. 0 31AC It, 0 25AC irk 0 28AC 186 0 25AC1886 0 37ACY17 I ISAD149 0 70ADI61 03940162 0 39AD16I 2 090AF106 0505,114 195AF115 295AF116 295AF117 295AF121 060AF124 065AF175 065AF126 065AF127 0.65AF139 040AF 1 SO 060AF 70 1 95Al. I 042

3 75AST. 1 25AU106 695413113 695BC107A 011BC1076 oilBC1ON 0108010611 012130109 010PC10011 012801091 012BC 114 0 11BC.116A 015130117 019BC 119 074E10175 075BC 139 02090140 03111(7141 025134 I4.'0 2113( I I 024

10 1 11 012IN 1100 0098C14811 00913C144 00913C157 01280158 009EI0159 0091301744 009130177 015BC178 015BC182 010BC1871 01013018.1 010

1,1831 0091101841111 00980204 0 108020713 0 13802016 0 1313C212 009BC2121. 00900213 0091302131. 0098(214 009BC214C 009PC7141 009802376 00900238 009130239 0 12BC2514 012802525 01580258 0 2513025134 0 39002284 0 3013C300 030FIC301 030BC 303 02613030713 009PC327 010E10328 01013C337 1. 1080338 00980347/1 013BC461 0 35BC478 020130527 070130547 010130548 010BC549A 010BC550 01480557 008805578 00013(558 0 10808335 1 60817115 030E301248 0 59817131 04280132 0 4280133 04080135 03080136 03080137 032130138 03080139 0 32017140 03000144 I 10130I500 029BD I59 06511000 150130166 095130179 0 72110181 0 450018.' 07080183 0 70340201 083130.70:. 0 6580203 0 78B0204 0 70130:127 04600273 0 5980775 040

50232 0.35-: 233 0.35

34 035.36 049

37 04018 04042 06546 075 '6 032:10 065:14 065:17 0 75

0750 065

06597 095

./19 0451 25

92 1 25)7 090

A37 150((1115 03510119 0 3507119 06587127 0 3913F154 02081158 0 2281160 0 27BF167 C27131173 022BF177 038BF178 026/31179 03461180 029111181 0291(07182 029

43 029U14 028u-15 028

4 0110I1

:36 0I197 011

:'98 0160 14

'00 04041 015'15 030'57 028'58 0 78

9 02871 026'73 018(16 0341.17 0 29

1.18 0 370.5 037:67 038:63 065

1)1.171 02501394 01900427 0 32BF457 0 3281458 03611(159 0 3691467 06881494 0 4510495 0 45131595 021411597 0 25871139 0 239F081 025BERM 0 30814190 1 50(11991 1 75

131142 0.35131343 035B1W92 08581025 0 5581084 02613F08' 0.321314.36 0.30BF 060 025BFV50 0.21BP.'S, 0.210PV52 0.2581590 0.7781V48 1 75B41Y.39 0451311100 026Balm 04980103 0 55BRC4443 1.1580100A0 20.55BT1O6 149BT116 120131119 3.15BT120 1.65BLI105 1.95B UI013 1698U124 125BU126 1.608U204 115B UM, 1.3081./2011 139BUMS* 15213U201313 1158U3276 1.20BU407 1.2413U500 2.259UI,088 1.9513U526 110BUBO,/ 2 25BU16913 1.70MJ3000 198MJE340 040MJE520 044MPSA13 029MPSA97 030MRF237 4.95AIRE450A 13 951411-11453 17 50MRF454 26 5010111455 17.50MR1475 2.951,11-11477 13 501.1(11838 13.9592.15W 4.50/C23 950

.,C25 15026 1.50

,c28 5.50K.29 450IC32 5.50(042 1.50,c44 1.25K-45 1.00,c.70 1.00,(771 0.75(C72 2.50

1.501.00I.50

1210450

n.....500 4.50OC201 5.50(,C205 10.00(1200813 1 45R20106 145

R2372 058R2323 016R2540 74911C.416334 0.9000816335 0.10SKESF 1.45TIP29 0.40111,29C 0.42TIP30C 0.43TIP31C 0.55TIP32C 0.42TIP33C 0.95TIP3413 0.95TIP4 IA 0.45T1PMC 045T1P42C 0.4711(147 065TIP120 0601113125 0.65HP142 1.78TIP161 2.95TIP2955 0.851183055 0.55T199. 0.20001067 1502141308 1 357142719 0.25

029040140019052012

J 0.120.120.200.12

.143708 0.121143733 9.502143733 2 752143792 1.352514477 1 952144444 1.15214529.1 0122145796 0.482145298 aso2145485 ass2145496 ass2SA715 aso2SC495 0.0020C496 080ISC1096 aso25(1106 25025011728 22025C1173 1157SC 1306 1.402501307 2.952SCI364 1502001449 00025(1678 1.252SC1909 1.2525C1945 3.752SC1954 0.952501957 011025C1969 1.9525C2028 1.152502029 19525(2078 1452502091 0852502098 29520(2166 1 952SC2314 01020C2171 0362SD: ... 0.503506., 095

DIODES

54119 080114115 01304145 0 161,4148 0179415-1 006H5156 0 15

030:1601,1 004HAlos 012111110511 030

0 790 100110 Is0 451 200 630 550 350400 14

138208100 033138710 800 0.33139723 090139290 400 0 2208299 80p 0 7295810 02005 636 'sop

0208v 638 60013

060BY 855.600 030138071 600 1 7507995030 0 35CS4B 800CS107 16 500847 0 150490 0 100591 0150A95 0 1005202 070IN21130 5001147.113 5001N23C 500IN23ER 500IN23WF 500

(814001IN4003IN40040440051N4007IN414804444810154010454070454031N5406

N5308

ZENERDIODES

04

OS

0506021012

1412131616

041520

0 10

LINE OUTPUT TRANSFORMERS

DECC A 100DECC A 1700 MONODECCA 1730OE CCA 2230(,EC 2040

7.959958 9S8 25

95.3RuND1G 1500 15.45GRUNDIG 5106010 2222 5011.6011

13.45.7 T CvC20 820

T CvC30 825PHIL IPS GB 850PHIL IPS 09 899PHIL IPS G I 1 13 99OVE 725 10.95HUM T204 12.40110408780E 90' 11.15TFLEFUNKEN 7118 11.15THORN 8000 23.50T11OR/49000 9.95

HORN 9800 22.40

CATHODE RAY TUBES Please add E3 additional carriage per tube.(ME822,31 19.00CME822GH 25 00CME1428GH 45.00CME1428W 3900CME1523W 39 00CME1431GH 39 00CME1431W 39.00CME202GH 45 00C64E2024W 45.00CME2325W 45 00C5463218W 45.00CME3132G1-1 45.00CME3155W 45 00CRE 1 400 25.00CV1450 35 00CV1526 19 00CV2185 15 00(V2191 19 00CV2193 15 00CV5119 85.00CV5320 85.00CV0389 55 0009-110011 39 50010.210GH 45.00010-2106H688 65.00010.230011 35 00010.230GM 35 00010293-GT 90 55.00013-300H 49 50013.51GL 26 85 00013-511764 26 85 00013 -45tH 01 55 00013-610011 59 00013-511011 59.00013-611GM 59.00013-630011 59.00014.1500(1 75.00014-150GM 75.001314.1620H 84 59.00014-172011 55 00D14- 172GV 55.00D14.173G1'l 55.00014-173GM 53.00014-17300 55 00014-181GH 98 65.00014.181G) 55 00014.181GM 53 00014-181GM50 59 00014.182011 59.00014.2008E 89 00014-2000A50 85.00014-200GM 75.00014-210011 75 000314-270G14 50 75 00014310W 110.00014-320614 82 85 00014-340014'KM 45 00014-340158 45 00016-1000H 65 00D16-10061-1.65 69 00

UP 7 6 35.0001413 78 35.00F16-101GM 75 00F16.1011.0 75.00F 21.130GF1 75.00F21.130LC 75.00F31-10GM 75.00F31 -10G14 75.00F31.10LC 75.00F31-1OLD 75 00F31 -121D 75 00F31.13GR 75.00F31-1310 75 00F31 -131G 75.00F41 -1231C 185.00F41.1411G 185.00F41.142LC 185.00647-120W 19.00M7.120GF1 19.00M14-100GM 45.001.414 100LC 45.00M17.151GVR 175.00M17.151GR 175.00M19 -100W 45 006419-103W 55.005423-110644 55.00M23-11110 55006423-112GM 55.00M23-112GV 55.00M23-112GW 55.006423.11264 55.001924-120GM 59.00M24.120LC 5910M24- 120WAR 59.00M24.121GH 55.00M28-12611 55.00M28.131C 4900M28.13LG 49.00M28-1300 49.00M28 -131G41 55.00M213 -1330H 55.00M31.101GH 5590M31 -1820R 5500M31-18200 5310M31 -184W 6510M31-184GH 8590M31-184831 65.00M31 -185W 69.00M31.190GH 55.006431.190GR 55.006431.1901A 55.001431.191GT 55.00M31 -191W 45.00M31 -220W 59.00M31.27005 65.00M31.271 P3165.00M31'271GW 6510M31 271W 65 00

M38 10.10H 65 00M313.120W 65.00M38120WA 65.00M38121G1-101 65.00M38.121LA 65.006438-122GW 65.00M38.14OLA 65.006438-1421A 65.00M38.341831 65.00M38 -344P39 65.00M40.120W 5900M43.1216 01 65.00M44.120LC 65.00M50 -120G14 65.00M50-120GR 65.00M50.12OGV 65.00M50.120LC 65.00SE3A P31 4010SE44) P7 45.00SE428831AL 55.00SE428P31 55.00SE5FP31 55.00¶94814 65.00V5004LD 59.00V6048CAL 59.00V6048J 49.00V60648831 55.00V6069GH 55.00V6070831 65.00V7030 59.00V7031GH 59.00V7031 67A 5900V7035A 49.00V7037GH 45.00V8004GR 65.00V8006GH 65.00V80108 65.003881 11.503081 11.503HOBM 55.003WPI 18.504EP1 30.00513H81 30.0058HP1FF 30.005B1'1P31 30.00SCPI 10.005001A 15.0066 PAS 390012CSP4 45.0013881 13.50138884 17.5017DWP4 25.0032,1 1085 69.001273 39.001564 45.001844 80009442E1 751095447GM 75.0095449GM 75.007709631 78.50

D16100G.67 65 00D16-- 100G11H /79 69.00D161006/1.97 65.00

SPECIAL OFFER

WIREWOUNDRESISTORS

016160GH 69.00D21-10GH 65.00DG7-5 55 00DB7 6 55.00087 36 4500DG7 32 45 00

High Resolution Plillips 12M31 -325GH f35.00 each

C0115 + trans available

4 wail 2144.1015 0207 woad 1147.22/5 02011 waft 111. I 51( 0 2517 wag 1R15K 030

17013 2 45 000143-91 55.000117 91 45.00087.5 35.00

M36.141W 75.001936-17010 75.00M36-101GH 65.00

VIDEO SPARES & HEADS

VIDEO HEADS31155Sugable fix 400JVC andFerguson/no/30s 29 SO

311551111 Sudade to, HitachiVT5000 VT8000 VT76000 VT050:VT7000 33 954HSS SudebIe lot most NalonalPanasonoc Models 33 9541-45S(UIN:Sugabielo: PanasousModels 370 and 380 33 95

BETAMIX VIDEO HEADSPS31311 Pon. Suslatae to, Sony 4101Toshiba 5000 Seoes Ind NECP07400 3esoRS0.3-13 SudabIe Ito Sony 51. 8000511080 SI D7ME 3950DSR10-R Suotable 4, SVI,,, St C5SLC6 51C7 39,50Sanyo Head nor01C93009500 4910Sanyo Head 'or VIC5300 5000 49.50

VIDEO BELT KITSA0,0 V59300 951;. 5.01,0 071 5500 J 759890 3.75 51080 OK 9300 3.75153911sue 3016 4.50 Sanyo VTC 9300P 190ToCIIHR 3330 3600 4.50 Sharp VC 6300 375'VC HR 3360 3660 4.50 Sharp VC 7300 3.751P.10.iS0.1. NV 300 400 Sharp VC 8300 3.75l'ar1ds0116 NV 20008 3.75 Shaw VC 9300 375;`,.04,00,t 300013 3.75 Sony SL 300013 1750.05:5:419 NV 7000 3.50 Son, SI 8000 8080 4.50

5001 tit C11. 400175 450

SANYO ORIGINAL VIDEO PARTSSANYO ORIGINALPART NUMBER 111013EL DESCRIPTION4.579 108008 vIC5150 86.3.3 Mono: 3 615 9 954 5277 23501 VARIOUS 640101 Assy 9 754-527V-51000 5150 Capston MoIo, 29 95143-0-4904-00900 101113615 Dear 101e, Assy 5 95143.2-457T-05900 VTC9455 Sloppy Reel 83'.,' 0 55143-0-545T-01701 VARIOUS Pinch Holm As',, 8 951430-5451.01700 VARIOUS Pinch Nolte' As, 195143 0551T.5/K9300 1d4': 455, 0 95143.0-661T-03800 VARIOUS 10.0105, 0.95, 095143.0-6621-01201 8.50143-0-9974-00100 195

Video Head Cleaning Tape (VHS Automatic weadry I 6.50Video Head Aerosol Cleaner 0.85Video Copying Lead and Connector Kit Z/V.

VIDEO ALIGNMENT TAPES49 5049 50

E N T MULTCPLIERS VARICAP TUNERS PUSH BUTTON UNITS

TT : ' 1 ' 635ITT C01730 6.35PHILIPS GO 550 6.96RANK 1204 6.91THORN 3000,35, 7.57THORN 8500 800THORN 9000 800IA_0051-1-1,41 111,, .. 5 45

ELL . -1 . 3. mu, . 4130 865ELL 104.1961AUL c ARC/ 8651)321 8251,1:7 13 25

.`100A ITT : 55 22,5, 795:TT 00:05' WAY 10 19PHILIPS G8.550, 6 WA: 14 49

u ...-11100 200MA QUICK BLOW FUSES

THERMISTORS tip emh50 each

REPLACEMENT

ELECTROLYTIC CAPACITORS

00 23

230

20MM ANTI SURGE FUSES

0 4955

025,,I..4 , ,11....., 15p each

'A //130 12p eachYE CCA 301400400.50( 285YFCCAI30 1001400 ./05: 299.0 CCA 1700-00.200,400.35001 3.55,EC 2110 .600 300V, 225

ITT C0C201200 4008, 1.80PHI( IPSO (60030059 225PHILIPS G9 .2200.63V. 119PHILIPS 011 .470 2505. 235

SPARE & AIDS

HE AT SINN COMPOUND 100FREEZE IT 095:.;01 DA MOP 0.64SWITCH CLEANER 0.85W040 175

1. 33. PULL MAINS SWITCH.0EL0 A DEC RANK THYF1NETC I 1.02Pv E IF GAIN MODUL E e99ANODE CAP 7,5' 069

2 i ELECTRONICS & WIRELESS WORLD

PHONE0474 60521

4 LINES

P. M. COMPONENTS LTD TELEXSELECTRON HOUSE, SPRINGHEAD ENTERPRISE PARK 966371

SPRINGHEAD RD, GRAVESEND, KENT DA11 8HD TOS-PM

A SELECTION FROM OURSTOCK OF BRANDED VALVES

41714 24.5041834 7.50

(IllEB1s3 0 70

A1998 11.50 (8(93 09542087 11.50 EBI. I 250A2134 14.95 (13121 20042293 6.50 EC52 0 7542426 35.00 EC70 175A2599 37.50 EC81 7 9542792 2750 EC86 10042900 11.50 EC88 1.00A3042 2.00 EC90 11043283 24.00 EC9I 550AC H DD 4.00 EC92 1 95AC THI COO EC93 150AC T22 5975 EC95 70088271 39.00 EC97 110AH238 39.00 EC8010 12 00ALSO 500 ECC 32 350AN1 14.00 ECC33 3 50ARP12 070 ECC35 3.50ARP34 1 25 ECC81 1.5040035 2.00 EGGS' Spec a,AZ t 1 4.50 Ouality 2.25AZ3I 150 ECC82 0.66131.63 100 ECC82 P51,11,BS814 55.00 1.95BTI7 25.00 ECC83 085C1K 27.50 ECC83 8710,a,C317 22 00 1.35C3JA 20 00 FCC83C64 saw 1 95C1108 65.00 ECC83 Siefrol,C1134 32.00 250C11484 115.00 ECC85 0 75C11491 19590 EGGS& 2 75C11501 135.00 ECC138 095C1534 32.00 ECC91 200C3E 2950 ECC180 072CC31. 0.90 ECCI89 195C81006 3.50 ECC801S 695

CV Nos pry, ECC803S 6.95Or r(IlArss ECC8074 060

038 27.50 ECC2000 795063 120 ECF80 1 150441 22.50 ECF82 1.150442 17.50 ECF86 1.70D490 4.50 ECF200 I 85COMO 125.00 ECM/ 1 85DAF9I 0.70 ECF801 0 85DAF96 0.65 ECF805 250DC70 1.75 ECF806 10 25OG90 150 ECH3 250DC X-4-5000 ECH4 300

25.00 ECH3S 350DET16 23.50 ECH42 1 50DE118 26.50 (07181 1 00DE T22 35.00 ECH83 100DE 723 3500 ECH84 1 00DE 724 39 .00 ECH2000 1 50DF 725 22.00 (0.80 050DE 729 3/00 (C182 0 79DF91 I.110 ECL83 250DF92 960 ECL134 0 74DF96 1.25 ECL85 0690(97 115 ECL 86 095D13133 1.20 ECL1305 069D1-177 0.90 EF374 250DH79 056 EF39 150DH149 2.00 1(40 4 50DK91 1.20 EF42 3 5013092 1.50 EFSO 250D135 250 EFS5 495DL63 1.00 EF70 I 20D170 250 EF7t I 500( 73 1.50 EF72 I 200192 1.25 ((73 100DL93 1.10 EE80 0550194 /50 FF83 395D196 150 EF85 050DLSIO 13.50 EF813 225DISK, 1000 FF17161Aelias,DM70 /50 450DM160 450 EF89 I 500051 1.50 EF91 195008687 975 EF92 21500802 0 35 EF93 0955551 49 50 E F94 095E803 29.50 EF95 195E811 12.00 EF97 090E820. 4.50 EF98 090F83CC 4.50 EF183 065(83F 5.50 EF184 065EB6C aso EF730 180E88C 795 EF731 350F88CC 3.50 EF732 350E88CC-01 EF800 11 00Mullaro at 6.95 118045 19 SOEI38CC EF8055 19 50SPecoaI 5.95 EF806S 19.50E9OCC 7.95 EF812 065E90( 7.95 E11200 1 50E9114 410 (1490 0 72E92CC 3.95 (090 095E99( 6.99 09511301 18.50 EL33 500F182CC 9.00 1134 250

180F 650 (134 Wu,:E1136F 8.50 F15147, 4 50EIBOCC 750 2136 1 95(280f 19.50 EL36 Mona':E283CC 12.00 2.50E288CC 17.50 (137 900EBIOF 2950(1148 1.00

(138 6506141 350

EASC 1.00 EL 42 200E452 35.00 (181 6 95EA76 595 (183 150EA79 195 ELBA Bons, 0.95EABC80 ass EL 84 /34,03. 2.95EAC91 /50 EL135 450EAF42 1.20 ELK 1 75EAF801 2.00 EL90 I 75(834 '50 EPP 600(041 395 (195 1 75(891 085 (1153 12 15E8C33 250 EL183E 3.50EB011 195 EL IBP 350EBC131 1.50 EL360 6 75EBC90 990 EL500 195EBC9I 0.90 EL 504 195(BF BO 0.99 EL509 525

6953 65

11821 850(1822 12.95ELL80 22 50EMI 900EM4 900EM80 0 70EM81 0 701084 165

85 3 952.50

15 001 954 50

235.000.802.351.505.95

,87 0500555500702752 750 750751 50295

4130 295I( 9002M 69520 900

17 500 17 50

3.48 175004E 17 50

6C12 4P 17 500086W 60030712013 500GN4 60006110 15 00

,5101, 40010C 16 50

054 12 001, 12 00

14 0013 00000

.1 2. 10035 DO17 5013 50

I 24 00-,355 14 SO

I 501502 502 502 504502504 50100

70 0 751 080

0751 501 OS4 95

70D 4003 50

DC 3 SO0 701 50

OD 3 SO4 00100300

85 0045 00

7 003 502004004005002 00

17 50

1950KT67 900KT n 00,11.

10 95Kid I 700(TSB USA 10 95KT88531.00

18 95KTW61 250KTW62 750KTW63 200KTZ63 25011022K 6951102 20 12 00LB7 70 95 001598 6 95M5024 60 00M5374 60 00M5143 155 00M8079 600M8062 750M8083 3 25138091 750M8096 30008098 5 501.18099 5001.18100 55008136 700M8137 795M8161 650M8162 5 501.48163 550M8190 450M8195 650M8I96 550M8204 550M8223 4 50M8224 200

M8225 3.95051401 29.50ME 1402 29 50ME 1501 14 00MHO 350MHI6 400AAL4 450171P25 195.00MS413 550MU. 350MI1.100 125 00N37 12 50576 985

1 15WA 250

2501.152.502.501.601.701 00300

Ss, 1 7577143 2 50'1150 3.95

2.502.500 75

56 0 750 0 75

350110

400 1.1000 1.2584 040115 055738 0 7089 0.70189 0.70805 0 70806 08082 0.8080 0.6502 0.60

754 96586 120

'8, 0407700 1807701 18035100 040

801 1 357802 0 857805 1 25

806 100808 1 25

0200 ISO02 0 8583 25084 0 7585 080

0 850 BO090

69 002002 503 003002 00

'. 42 000952501 751 500 72

'IA 0720 600 520 78

, w 00295

, 1 00i4S 12 50.0) 110

115'18 175

9 4 85,59 495

7352T 3507170 2 95

. 3357 2950'137 060

7033 050PY8I 0 70P062 0 70P083 0 70P088 065I 3e 5004 195'3300 0 79

not 0 7972 00

139 50595 00

495145 0065 00

1 001950795

35 0045 0019505 50

15.0025.00

3)71.

27.50A

39 50550042 501503 005 004 85

05108 4'7 40005150 15 6.9505150 30 :150015045 7000SI200 395051202 3 95051203 4 15051205 395051206 1.05051207 090

001208 0.900S1209 3.150S1210 1.50051211 1.50001212 120001213 5.000S1215 2.100S1218 5.000U37 9500003-12 5.7503/05.25 2.5001106720 29.5000087100 145.00002-2500 45.00003-125 65.00004-250 70.00004.400 76.00RIO 4.00RI6 12901357 15017110 2.50R19 150R20 12091569 55.00RG1.125 4.95RG1.2404 14.50RG372904 1501303712504 35.00Fil(282i 62.5000.208 12.0081.16 ISORP1.16 12.00RPY13 2.90RP1743 250RP0132 250RR3.250 15.00RR3.177,0 35.00RS613 45.00RS685 54 950006813 52 15S6F17 595S6(33 28 95011E12 38 00430 20 12 005104 10 10 00510916 15 009130 5 59SI3OP 5.95SC I'800 5.00SC11100 600SC1 120,, 5 00SCI 130'' 600SCI 200 900SPAS 500SU42 4 951132 5 3,7' 85.007132.303 45 00TB12000 395 00701.1004 25.007003. 101 35.00T03'12 4.00TDD4 550TP25 1.50TSP4 700nit 150sss, 45 00TT22 45 00TT100 69 00TTR311.117 65 00T02.1254 85 00TY4 400 85.00T08 600W

365.007052 250 37500U11120 2 751.119 11 95U24 200L125 090U26 090U37 9001141 6 95L/50 200082 300U191 0 70U192 100U193 065U251 100U801 0 75UABC83 06506142 I 00UBF8S( 060UBC41 225UBC81 1.50UBF89 1.00UBI 21 1.75UC97 1/0UCCX4 070UCC135 0.60UCF8U 1.001301421 120UCH41 150UCH42 2.50UCH8 I 1.000082 1.75UCL 83 2.50UF41 1.15UF47 1.15UF80 1.75UF85 120UF89 2.00U141 5.50UL44 150U184 1.500185 0.135UU5 3.50007 600UU8 900UY4I 150UY85 0.700235A 116 25900V238610 295 001/246420 315.00V240631K 225.00V241C 1K 195 00V339 150V453 12.00VL S631 la%0048 450VP133 200VR75,30 30000101 200V10530 1 50VR150 T. 11SVT52 250VU29 4 50VU39 150W21 450

W77 5.00W729 100W739 150X24 4.50066 X65 4.95x7601 1950C24 1.509C25 asoXFW47 1.50XFW50 15000,2506 75.00005.500 22.5001621317 7.50XNPI2 150)0711.16004 49.50081 32004 79.50881 0400A

149.500507 25.00065 6.95001100 75.00031060 265.00v11020 42.50011060 195 00015070 19600011071 195.00011290 65 00777 1207302C 12.00Z359 9007505S 15.007520M 4902529.4 60077000 3007749 0607759 19.852803U 18.95745000 12.50

1508 006008.00795

14 00900

10 009 00

7181283 4.00

1822 10.001827 55 00B354 45.00

58634 75.00ICI 2.50IC5GT 1501E131 2S01(1361 2.501,13GT 2501133 250IN? 450'NSW 2501P28 25001P39 19.50IRS 0.904174 100104 1.75105 1.001X26 140172 8 952ASISA 11 507137 15071327 69 507C39A 32 502C39134 39 507C40 37 00.'CO,` 29 50:C43 60 007C5I 0 75.'153 45 00.'405 1507D/I I 95202110 3157(22 49 002(26 7952342 93 002355 295.3021625 35007K25 R4016700

75.002021, 95.0071(77/ 250 00.9945 140 002056 250002%24 5.00:141076 12 0034 1086 9.0036109E. 110036 11011 12.0044 1411. 11.503A 1473 7.5034 16715 10.00:i434 3.95384 1 10345 4.503115 0.993472 3.35302 3.00304 4 95387 4503024 moo31326 24003028 15 003626 1.5037.4 1.0011,23 19.003C4S 14 003086 1 50319388 2.5031736 0.95300 2503GYS 1503Db 45030714 29 503172 49.503FH7 1953E37 195304 250304 I 753W4G1 2504135511 115 004.558 65 00

,2508 79.5044008 87 504 10004 425 00

4832 35 004E1074 1 7541326 1 954C27 25.004C28 25.004C35 145.004CX10004

425.004CX40004

1100.004C x2506 49.004C%2500 ((MAC

59.504032 125.004CX2508N 75004C 0250K ((MAC

95.004CX125C ((MAC

125.004CX3504 95.004CX350F 79.504XCI5008

3944504E27 599.004GS7 2254352 75.004JC64 29540E6 1.50401508 359056 1020 95054132M 900541636 10.00541706 6.2554.180M 900SA -2066 10.005408 2.1554618 1105494 2.0054U4 1505B I IOM 10.00513.254M 14.5050.2550 19 5050.2560 15 0056-25761 15 00513-258M 14 505C22 125 00SC184 2505.11800 2950.005941,0 5505E1460 4 95514 595SU4C, 2.955041,13 4 505V46 15050301 1.9557401 1506301:' 070662036 900647 4956481, 1.50bAC7 2.00(74G5 1506:67 19564116 1500A34 2006437 20064135 1.95641(6 250643S 0600804 3.25bAM5 6.0064M6 1.9564145 4.50041384 3.506A05 1756406 0 851,885 5 956455 1 506456 /5064571, 4.506476 0756418 1755404 2.006AUSt,1 450bAU6 0 956406 075bAW8A 2.50660467 1 95bAY3B 195bAZ8 4 50687 2800886. 1 506810 19561366 0956E147 450613484 350613E6 09:668060 1006131415 1956888 1 5061336 1 506064 400511(7A 195',1546 85 0061,4S I 1560133 115 006a.1.19 0 5866114 I 65014195 I 65171111- 45060136 3 956103, 0750137374 0.72664 77,74 3.955111, 0 704,1447 4 957,6301 2 15503010 7,15sff 550613014 150613100 5 35513W' 1507.0W8 4007081, 048,b071,T 3506676 2.5061317 2956C4 1 2561,5 1956C6 2.506095 1506011 2506018 2506044 4 9560,4' 350hCBS 39560516 I 95

600604 4 506CF6 1 506067 22560716 6 956013 3956016 3 2560184 1 506CN5 1 606CM7 2956CS6 0 756057 0956CW4 650606 2 5061:303 2356038 0 9560136 1506005 69560068 2 506D154 I 50bOW4 2156E5 3956E44 4956E47 2506E48 2506(88 1 756EM5 2506E137 2506E U7 1956E08 1 756F V' 2956(W1 2956(1777" 4506( I 2006(5 4956(6 2506F6G 200617 5506(17 1 506113 3006(14 1006117 2756(21 2506(23 0606(24 1 256E25 I 256(28 1 2515(32 1 256(33 17 006FG5 1 956F07 2956661, 5 506GE5 39561,1484 0806GK5 15061,136 I 9566M6 2656GS7 2156607 2 50&GM/ 2506GW8 25060'5 3956141 950bH3N 2 50656 1 95614661 1956515 5506HE8 25061456 49S6.14 2 156J4WA 3156.15 250516 200617 41S61864 4 506JEbC 6 50bJUB 2506JSOC 6 505171, 4 15613 74. 2006681, 300&KIN, 6506KM8 25061519 295511 2506115 3156119 3.956161,3 29561661 5 75616GCPhilos 650616GT 1 9501020 1156156 75061.6GA0 5.50SYLVANIA6118 2506106 6506071,1 12061170 3156.544 I SO6SA7GT 1356SC 7 I SO15SG7 25065H7 13565.176,1 1.20651(7 1 356SK 7GT 1.35651.7GT 085691,17GT 1356507 1.3557357 1.956U4GT 1.75bU6WA 3.506U8 1.156U8A 1.506V6G 1.2560661 110

1003 951 001 501 001 002 254 502 001 75I SO3 502 SO3 502 502 503 505 502 501 502 501 951 951 2S2 502950 75

952 500180 65

45 0055 00

5 503 951504 951 00125

15

2 501500651952 500 857952 503 95

954 501 50

952 95t 752 757 501 95

203 503 50

19 5038 003 954 504 503953 507 95

9550959575959550958595

4 SO3 203 203 202 50295

145 003 502 9S2 502 950 953 50600350

A, 3 50e 2S0

900

35 001,111:41 25 00

33 50900

0, 10 500 707 950 95

..ul'I 0 55201.3 06070P4 I 952005 I IS21376 495211 U8 37S2481 39 5015D068 2 95251667 1 75s' 008 1 75

AUDIO TAPE HEADS

MONO Hi Au 250AUTO REVERSE 3,95STEREO HEAD 150

VALVE AND CET EASES

84 3.951350 5.50870 0.25876 51070 0.25fAIG 1.505100 0.70898 0.3551971S6 H. 0.601346 0 7581543 0201313E 0.5013148 300OCTAL ass

5.31(406, 35 009K410 25 0041610 3500005UX7 I 7

VAL VE CANS67,00 69 035ANODE CA17,

a50009(87EOCKFT 10 00613 SOO. f '

8 50

19 50'506 650

17 040tl 148

0 95I 001350 95

.3 1 tO

4 1250 45obi)060

MR 100100

93 0 609 100

1, 1 2 5013 060, 1 75

5 5019 504 50200I 854 505 50695600

1 500 9S

1 15ISO2 95200

15 004 503 Sl/2 504 508 507503 006 502 50

15 003 50

13 5012 50900

19 SO15 006 50

10 00I SO6 502 SO245

25 00150

33 5015 00500

15 0017 508004 50

55 00800800

275 007S 006 506 95

14 9559 002 50

85 0015 0035 0027 5035 0014 SO95 00650

20 0060 005 509 95

13 951 001001 000 602 503003006 955 505 50400

10 9515 00

25 00950

250 004009005509502501951 953 25450

28 007 504503504503506 152502 502.502.501 852 955 753 259506 50350

11 0010 95500

13 95-,'5 39 50

9 450I 752 25

8516 003 653 793993752 294 50200

4 3257004 20850

3,4174 95010 50250950

72 0072 00

2 503206 456 952 504 50350450

14 50750850

.04 61 10 95

.0 Fil A 15 00650

11 509509 955 95250

'A 6502002503 953 507507.504 95

13 5015 00500

155 0085 008509 45

15 0029 SO47 005 50

29 5,7125 95

15 0010 SO1010 05I1 SC,

OVER 4 MILLON VALVES IN STOCK4.000 01118701 Types

Please enquire...5r types HA listedSpoGallv selected 4191 matched valves

avaable on request

CALLERS WELCOMEOPEN MON-THUR 9AM-5 30PM

FRI 9AM-5 OOPM'24 -HOUR ANSWERPHONE

SERVICE'ACCESS & BARCLAYCARDPHONE ORDERS WELCOME

UK ORDERS P&P f1PLEASE ADD 15% VAT

EXPORT ORDERS WELCOMECARRIAGE AT COSTPLEASE SEND YOUR

ENQUIRIES FOR SPECIALQUOTATIONS FOR LARGE

REQUIREMENTS



725

INSTRUMENTSCOMPONENTSEQUIPMENTACCESSORIES

Official orderswelcomed.

Export supplied.Please add 15'n VAT

(UK orders only)

---UK FREE DELIVERY

1_

OSCILLOSCOPESHAMEG20316 Dual ?OMR/ lwim ;iro 5es £314.00204 WWI MUD dell,' £418.00205 Digital storage dual 20MHZ P.0 .A605 Dual BO MHZ plus sweep delay £583.00CROTECH with component tester3031 Single 20 MNI 95cm CRT £199.00HITACHI V212 Dual trace 70 MHZ8 s 10cm £320.00GENERAL OSTSm single trace 5 MK'3 CRT £139.09HUNG CHANG Dual trace a ''620 Dual 20MHZ component Mil £295.00635 Dual 30MHZ Sweep delay £399.00615 Due: I5MHZ bat/Mains £399.00660 Dual 50MHZ Sweep delay £579.00

Add storage toy ur scope 200ksampling £195.00

COUNTERS AND TIMERS

220 2400 AC mains B digit LED

Counters DANZ resolution 5mV sensitivity10014111I 2 ranges £99.00600MHZ 3 ranges £126.001000M HZ 3 ranges £175.001500IANZ 3 ranges £199.00Timers 0.001HZ Resolution 100M NZ 5mV sensitivity0P10 Standard model £219.00O 11100 Inc) display hold etc stopwatch RPM etc

£285.00

243 0 24 volts 0 3 amps IX245 0 24 volts 0 5 amps DC154 5.15 volts 0 Owns DC

DC POWERSUPPLIES240V AC input Stabilisedvariable output voltagesDirect meter readingvolts and amps

£43.26£56.26£33.26

Also 1380 DC 3 amps max Freed !no meterl £13.000 300 158 DC with volt meter £29.950 3000 2 amps OC LCD display £150.00

GENERATORS 220 240V AC operas on

1:[RcliooFUNCTION sine so triangle ttr 0 PJ500 0 IHZ 5000111 £110.00TG101 00211Z 2000HZ £110.00TG I 02 0 2141 lo ?MHZ £160.00PULSE Square Complement 11'10 PTG105 911 To 5MHZ £105.00TV-VIOE0 PAL VHF UHF 55 6 65MHZsound carriers RGB and SYNC 0 P s AM FM sound mooColour etc £199.00

GENERAL EQUIPMENTxi nt m probe kin IThommo £10.00200 1001011 110MHZ R C OSC £65.17220 20111 2001HZ C OSC £78.22CM200 Bench Digital Cap Meter £89.00111301 LCD Digital Temperature £59.502018 Audio Power Meter £220.00VF501 Electronic Insulation Tester £65.00PFM2110A 200MHZ Pocket LED County £75.50OM 358 8 CH Scope Multiplexer £179.00&DMA 250MHZ TR 01P Meter £43.042016 IH1 !MHZ Generator 05 £180.00

DIGITAL MULTIMETERS3. digit LCD displays508 15 renal 200mA OC 2MEG £19.96 A105 14 Range 2A DC £21.505281 13 rungs. plus Hie tut £26.0455C 78 range IBA ACiOC £35.656010 28 rings 10A ACrOC. 20 MEG £33.507030 0 P. version of above £39.50578/0 range auto memory hold IDA AC OC £34.50615 19 range plus Hle test 20MEGICIA DC £30.395010 31 reale 10A AC DC buzz 20uA PC OC £36.50TM357 30 range 10A AC/OC buzz £39.005010 EC as 5010 cap He cone £52.13

SWITCH MODE PSU'sOpen Frame Models I/P 100/240Y AC00510l, 5v ladiustablei I Oarn[ £7.78Enclosed Model

BENCH DMM'S3 Oigit LCD IDA

AC/I)C2n meg Buzzer etc

322 0/h3210 0 1 True RPriS

£19.95

0 0

STOCKISTS FOR:

£ 89.00£119.00

ANALOGUEMULTIMETERS1015 IS range pocket 100 V £7.501035 19 range 2014 10A OC£10.3910281 19 range 10A DC Hle20Kv£12.61HC201 19 Rug. 20K,V 12A AC OCil 5.612020 29 range 10A OC 111e 2130 / V £19.0930101Z 24 range 10A OC buzzer 301 V £20.83155m 21 ranee 10A AC/BC 201 V £22.575050E 41 Range FIT 20Mi P £28.658308 2b Range IDA AC DC 300 V £25 17

MEN

At-

LCR METERTC200 18 range digilai Nanaheld tester

6 ranges resistance

Trances capacitance

7 ranges inductance £85.00_

PROBE/PULSER6108 ?OMNI Logic probe & bleeper C 1 6 . 95625 513MHZ Probe & pulse, 0 5141 SOOMI £22.9507 7010H/ LOCK probe £ 9.52

AC CLAMPMETERS *4,300 300 mps 15 ranges'6000 14 r noes1 Iv OHM £32.834300 Au orange Digital 300Amy rani test £85.00

and leads

DIGITAL CAPACITANCEMETER t, range ,L11 AJplW ZOOOMFDPush Outlan selection 160131 £55.00

Logic Andlysr- .asuiatiuri Testers TerllperitlUtt: Illetel5 Ser.urity Systems Public Addrt-, Communications TOols Computer Equipment TV/VideoAccessories (See Catalogue)

ORDER BY POST OR PHONE. OPEN 6 DAYS A WEEK FOR CALLERS.

HEnRY'S aPPRonics= 301 Edgware Road. London W2 I B N. 01-724 3564n 404 Edgware Road. London W2 1E0 01-724 0323

TELEX 298102 TRANS G

EDUCATION AND ACCOUNT ENQUIRIESENTER 43 ON REPLY CARD

FREECATALOGUE

01-258 1831

3 WORKING DAYSEXPRESS SERVICE.

II 10/14 WORKING DAYSSTANDARD SERVICE.I LONGER TERM SCHEDULES

AVAILABLE.

CRYSTALS (FASTAEL Crystals carry full specifications

for most Communications Equipmentused today.

For further details contact the Sales Office.

CRYSTALS LIMITEDGATWICK HOUSE HOR- LEY SURREY ENGLAND RH6 9SU TEL. HORLEY (0293) 785353

TELEX 87116 & 87180 AERO G CABLES: AEROCON TELEX HORLEY FAX 0293 774658


TIME WRONG?MSF CLOCK IS EXACT

8 DIGIT display of Date. Hours. Minutes and Seconds.SELF SETTING at switch -on. never gains or loses. automatic

GMT/BST and leap year, and leap seconds.EXPANDABLE to Years. Months. Weekday and Milliseconds and

use as a STOPCLOCK to show event timeCOMPUTER or ALARM output also, parallel BCD (including

Weekday) and audio to record and show time on playback.DECODES Rugby 60KHz atomic time signals. superhet receiver

(available separately). built-in antenna. 1000Km range.LOW COST. fun -to -build kit (ready-made to order) with receiverONLY £89.80 includes ALL parts. pcb. 5x8x15 cm case. by -return

postage etc and FREE Kit News Get the TIME RIGHT.

CAMBRIDGE KITS45(WU) Old School Lane, Milton, Cambridge, Tel 860150

IEEE 488 CONTROLLERSfrom M A Instruments Ltd

IBM PC and Compatibles including Amstrad PC1S12.Half lencfh Interface card. software including Turbo Pascal or Quick BASIC interlacecable anc comprehensive operating manual. C295

Acorn 'B' and MasterInterface in separate case. software in PROM. IEEE 488 cable and comprehensiveoperating manual. £250New software for existing owners of Acorn GPIB controllers which otters compatibilitywith the new IEEE 488.2 standard. £28

All controllers offer a command structure which follows the 'IEEE 488 2 standard. Thissimplifies the control o existing GPIB devices. reducing the number of commands

needed and is com Natible with new devices using IEEE 488.2 format commands.

Designed. manufactured and supported in Great Btitain

For more information contact

M A INSTRUMENTS LIMITEDMoordene Axtown Lane, Yelverton, Devon PL20 6BU.

Tel: (0822)853585Prices exclude VAT and delivery


726ELECTRONICS & WIRELESS WORLD

68020 cache designOn -chip cache memory increases performance but its sizeis limited. An external cache with 25ns rams takes care of

much larger repetitive loops.

Acache is a high-speed memory local tothe microprocessor that holds themost recently executed instructions

or data. Being closely coupled to the micro-processor, cache memory can be accessedmuch faster than main memory.

Studies of modern programming techni-ques show that programs spend most of theirtime repetitively executing a few tight loopsof code. Cache memory speeds up executionby holding loops just executed so that whenthey are used again they can be accessedmuch faster than if they were held in mainmemory or back-up storage.

With the 68020, small loops of code arecaptured efficiently in the 256byte on -chipcache but performance can be increased stillfurther by adding an external cache to holdlarger repetitive loops.

A fast external cache increases perform-ance particularly when low-cost dynamicram is used for main memory. Access time ofthe dynamic ram is relatively long butrefreshing and propagation delays increaseoverall access time even further.

When an external cache is used, amemory -management unit can be added to a68020 system without performance degrada-tion. With no external cache, adding a pagedmemory -management unit such as theMC68851 for example can cause the intro-duction of an extra clock cycle when acces-sing external physical memory.

Adding a large external cache allows theprocessor to execute considerable amountsof code from the cache without having toaccess main memory. Using fast static ramfor the cache, no wait states are needed soprocessor operation is as fast as possible.

Size of the external cache has a great effecton the hit rate, i.e. the percentage of timethat the processor is executing from thecache as opposed to main memory. FromFig.1 you can see that a considerable hit rate

_ 80

1- 40

.o.ammi-; 2 4

CACHE SIZE (K.bytes)

Fig 1. With a 4Kbyte cache, the processorexecutes from cache memory about 80%of the time.

DAVID BURNS and DAVID JONES

Tag

Access address

Tag, M bits

-- M bi ts

VALID

If HIT and VALID ore not both active,data is fetched from memory

Comparator

Comparator

Fig.2. Each data item in the cache has an associated tag entry to allow the data to beretrieved. In a fully -associative (content addressable) cache, the tag entry holds a fulladdress and control bits.

Set size=2=number of tag entries per index fieldAccess address

Tag

broup0

Tag Data V

ComparatorHIT

Compar2to

Inde7:zr bits

1 of 211

VALID

Group

Tag 1:fa V

Fig.3. Using low -orderaddress bits as anindex :o a group oftag and data itemsmakes set -associativechaches cheaper.Fewer comparatorsare needed and thereplacementalgorithm can besimpler.


Access address lm bits)

Tag, t bits

of 2

Tag

Comparato

Index, n bits

Decrease number of comparators-split address into tagand index fields

m.tn

VALID

Data to c p

ARTICLES IN THE SERIES

68000 family architecture

68020 architecture

68020 extra instructions68020 display processing68881/68882 floating-point

coprocessors68851 memory -manage-

ment coprocessor

December 1986pp106 109January 1987pp103-106February pp209-212March pp333.334May pp535 -537

June pp614 616

vo=2-11v3114361-68020 addressand control lines A 15 A14 1A2 lAt lAO

Tag

1 of 8K entr

Buffers

Tag

Valid bit

es

ComparatorCACHE HIT

Update control logic

Index

32 bit data

1 of BK long -worddata entries

BufferenableData bus

(32 bits)

Buffers

6 8 020

1.

DSACK01

DSACK

BERRY

HALT

Controllogic

DSACKQ3

DSACKi

32 bit data

ENABLE

UPDATESTag ram

1,2

32 bit address bus and control bus -

Cache hit situation I Retry cycle request (cache miss) 2 [Cache update (retry cyc el 3

TSIZE0

1

N/CN/C

A14

ITEN

AT4

WRITEN

A15 TA2218 16 14 12 9 7 5 3

F244

2 4 6 B 11 13 15 17A15 A22

,`1423

Tog address bus

1A27 23 TA19

30 -27 -22

r

TA30 TA31 TF Co -.2 TS1ZE -1

F 244

A23 430 A31 FC0 -2 SIZEO-1

r

Logical address bus

Control bus


Fig.4. Direct -mapped caches, top left, useonly one comparator and replacementalgorithms are unnecessary. A block thesame size as the cache is produced by theindex field so there is only one group.

Fig.5. Cache design for the 68020 using32Kbyte organized in 8Kbyte long words,top right Cache entries are held in

32Kbyte of data ram while tag data withvalid bit is held in tag ram.

Fig.6. When a cache hit occurs, data fromcache ram is placed on the bus but when amiss occurs, halt and bus error signals aresent to the processor to make it retry theprevious cycle. This is to allow time forcache updating.

Fig.7. Using 25ns static rams a very fastcache can be made. The tag field consistsof ram accessed by the address andcontrol bus.

A24A TO

425F138B

A2612

AS

CPuSPACEEN2

FC0

FC1

FC20 C

A

LR

VALIDOUT

Gtid bit ramtag ram)

A2-14 1101

Fig.8. Simplified cache control logic providingenable,disableandclearfacilities.

can be achieved using a 4Kbyte cache.Increasing the cache size further results inonly small improvement.

In a typical cache, each data item, be it 8,16 or 32 bits, has an entry associated with itcalled a tag field, Fig.2. This tag fieldcontains information that allows the data tobe located.

In most caches the tag field contains alarge proportion of the address bus, thefunction codes and a valid bit indicatingwhether or not a data item has been enteredand is valid. Differentiation between userand supervisor address spaces is provided bythe function -code entry.

There are three basic types of cache - fully

5 16

A22

16

2

9

17

TA 57'

11

7TA22

04=1319

68 020

WRITEN

CPUSPACE

611

Logic address bus

Tag address bus

A31 18

FC 0

FC12

SIZE°1

TA31

16

16

12

9

17

Contra) bus TFC0 *TFC2

7SIZED 6

7t.L.

IA=

m[74tS2'

3

A30

-1-B

'C 74F521

0A.B

A23-

A30-_

6

2

9

7

VALIDOUT

CACHE_E

5

iii5V

17A0 BO -4D

15

13

11

6

24

47 CA -9 D"

mc7LF 521

19

-4

associative, set associative and direct map-ped. Figure 2 shows a fully -associativearchitecture in which the tag field containsthe complete address bug and function -codebits.

Each tag entry has an associated compara-tor. When an access begins, the presentaccess address is compared with each of thetag fields and if a match is detected (a hit), itindicates that the associated data item can beused for the cycle. Because every tag has acomparator, the tags can be compared inparallel which speeds up the process.

By using the whole of the address bus as atag there is no interdependence between thedata items, unlike direct mapping, and sothe hit rate of this type of cache will be veryhigh and related closely to the physical sizeof the cache.

When a miss occurs, i.e. there are no tagmatches, the cache must have some means,1f updating the entry so that it will be validthe next time that that address is accessed.To do this a 'least recently used' algorithmdetermines which entry when overwrittenwill least affect overall performance. Whenthis item is updated, the tag field becomesthe information currently on the address busand the valid bit is set. The next time that theaddress is accessed a hit will occur.

Performance of this type of cache dependson efficiency of the replacement algorithmand relies on the fact that there is nointerdependence betwen entries. On theother hand, fully -associative caches are ex-pensive because of the number of compara-tors required and the complexity of thereplacement algorithm.

Set -associative caches are cheaper. In-stead of holding the whole of the address inthe tag field, the set -associative caches use anumber of low -order address bits as an indexto a block of tag and data items, Fig.3. Thisindex selects a tag from each group andcompares it with the current access address.If one of these entries hits, the associateddata entry is extracted.

The advantage of this type of cache overthe fully -associative type is that the numberof comparators required is only equal to the

ELECTRONICS & WIRELESS 5511Iti I) 729

number of groups (or sets) and not thenumber of entries. Size of the index field,and hence the number of entries per group,is thus a trade-off between the number ofcomparators and the cache hit rate. A re-placement algorithm is still necessary forset -associative caches but a simpler round-robin type algorithm can be applied insteadof the least -recently -used one.

In a direct -mapped cache the index fieldproduces a block size that is the same size asthe cache itself so there is only one group,Fig.4. As a result, only one comparator isused and replacement algorithms are un-necessary so this is the easiest type of cacheto implement and the cheapest.

Hit rates of direct -mapped caches are stillquite high (proportional to the number ofentries) but their performance is degradedby address interdependence. This inter-dependence is caused by the fact that theindex field produces an offset into the cachewhich remains the same for addresses whichare modulo with this index, i.e. they have thesame index but a different tag field.

In execution this means that an entry canactually be replaced on the next cycle if thenext access happens to have the same index;there is no way of determining when theentry was last used or how frequently it wasused.

CACHE DESIGN EXAMPLE

A diFect:mapped cache for data, supervisorand user accesses to and from memory iseasiest to implement. Cache size depends onthe hit rate required and how much you areprepared to spend on fast static rams but istypically 4, 8 or 16Kbyte; in practice,32Kbyte is usually the upper limit.

Since the direct -mapped cache can beused for data accesses it should be designedto avoid stale -data retention. Stale data isdata held in the cache from a previous readcycle; it represents data in memory that hasbeen modified by an external processor writecycle. To prevent stale data, data from theprocessor is written simultaneously to boththe cache and external memory on everywrite cycle. Data read from the cache is thenalways the latest data. This method is calledwrite allocation.

Consider a 32Kbyte cache for the 68020organized in 8K long words (32 -bit words),Fig.5. Cache entries are held in 32Kbyte ofdata ram and tag data with the valid bit isheld in tag ram. The tag field could be 22 bitswide consisting of 17 high -order bits foraddressing an individual entry in the 8Klong -word block of memory, three function -

code bits to distinguish between the types ofmemory access, and two size bits for accom-modating misaligned data transfers (mis-aligned data is 32bit data not resident on a32bit boundary in memory). The valid bit isset each time an entry is made in the cache.

On a cache hit, associated data is readfrom the cache data ram and placed on thebus. Logic i.cs control the data transferdirection to and from the tag and data rams.Address lines Ars-31, function codes Fc0_2 andsize values size.0.1 update the tag field andinformation on the data bus is placed in thedata rams.

Ideally, cache updating should occur

while the read cycle is executing. For thispurpose, if there is a cache miss during aread cycle a signal must be produced earlyenough in the cycle to be fed back to thecontrol logic. This signal places the tag anddata rams in write mode, allowing datapresented on the buses to be routed directlyto the tag and data rams as well as to theprocessor.

This entry -update method is practical forprocessors operating between 8 and 10MHzbut for a 68020 operating at between 20 and25MHz with no wait states, the time avail-able for entry updating may be too small. Analternative method could be to use the 68020late -retry facility during cache misses asfollows.

When a cache miss occurs the cache -

control logic sends halt and bus -error sig-nals to the 68020 simultaneously. Thiscauses the processor' to retry the previouscycle, allowing enough time to enable thetag and data rams for writing. On executionof the retired read cycle, data read frommemory is written into the data rams andinformation on the address and control linesis written into tag ram, Fig.6.

IMPLEMENTATION

The faster the 68020 becomes, the moredifficult it is to design a system operatingwith no wait states. Therefore to gain anynoticeable performance improvement froman external cache, very fast static memoriesare essential. Fast and ALS logic familiesmake it possible to design a 68020 cacheusing 25ns memories without resorting tocustom or application -specific (asic) devices.

Logic required for the cache divides intofour parts for entry updating, general con-trol, tag -ram operation and data -ram opera-tion. Figure 7 shows tag -ram logic with 16Kby Obit 25ns rams. During a read cycle,addresses presented by the processor areused for indexing into tag ram, output ofwhich is the previously described 22bit tagfield. Provided that certain other conditionsare met, if the 32bit comparator indicatesthat tag ram output matches the currentaddress and control lines the cache -hitsignal arrr is asserted.

Conditions that must be met before ciiican be asserted are the true states of the validbit and cache -enable signal and the untruestates of the i/o enable, cpu-space andram -write signals. These conditions feed thelast comparator stage.

On detecting a cache miss the controllogic causes data presented on Da_31 to beplaced in the tag rams. During the cache hitthe F244 latch outputs are high impedance,thus isolating the address and control busfrom the rams to prevent bus contention.Data -ram logic is similar except that fourF245 bidirectional buffers are used for bothisolating and directing ram data for writing/reading; data direction is controlled by iii

Signals produced by the entry -updatelogic are described in the panel. This logiccan be implemented using simple two -inputgates and D -type bistable devices from fast orALS families.

Control logic can be implemented usingthe same simple i.cs; its complexity dependson the cache facilities required. For exam-

R/W

AS

CHIT

CK

2xiCK

SACKO(EXT)

DSACK1 (EXT)

Sequentiallogic

C MIS

FORCEW

WRITEN

INHIBIT

DSACK0

OSACK1

HALT

BERR

ENTRY -UPDATE LOGIC SIGNALSCMISS. Active when MAT from the tag comparators isinactive, this signal indicates a cache miss. It should besampled during the middle of the 68020 sj clock cycle.For this the 2. CL K input is used since it is twice that ofprocessor clock CL K.

DSACK(EXT)0.1. These are osxoco signals returnedfrom the external device during a read cycle (R.7 high)when there is a cache miss.

RESET. Connecting the processor reset line into theentry -update logic ensures that the cache operates inits correct mode after reset.

DSACKai. Cache control logic sends these signals tothe processor on assertion of address strobe A so theentry logic assumes a cache hit on each cycle.

HALT, BERR. On detection of a cache miss, cmiss isasserted then these signals are simultaneously sent tothe 68020 to make it perform a retry cycle.

WRITEN. Feeding the ram write -enable pin (w i directly.

this signal allows data to be written during the retriedcycle. It is produced from bsAckirno , and asserted onor close to the tailing edge of s4 of the processor clockDuring s4 the processor latches data.

FORCEN Data ram isolation buffers are enabled bythissignal to allow them to route data during the updatecycle.

INHIBIT. Produced within the update logic, this signalinhibits retry cycle for a cache miss.

pie, consider logic providing cache enable,disable and clear facilities. The valid bit isheld in ram with a clear facility which allowsall cache entries to be cleared.

In its simplest form, the control logiccontains a bistable device which can beaddressed by the supervisor when perform-ing a c.p.u. access to an otherwise unusedc.p.u. function (that is not access levels,breakpoints, interrupt -acknowledge or co-processor space). This access is treated justlike a normal memory cycle. Onec.p.u.cycle causes the bistable device toenable the cache through cAcne_g. Anotherlocation clears entries in the cache by clear-ing the contents of valid -bit ram and a thirdlocation causes the bistable device to dis-able the cache.

Figure 8 is a simplified control -logicdiagram. Signal CACItE_E is used in the com-parator section as vAmoirr; both signalsmust be asserted before a cache hit is con-sidered valid.

When the cache is first enabled or a cacheclear command is issued, the valid -bit ram iscleared. Using the address lines shown,cache clear is initiated by a memory cycle ataddress 107000016, cache enable at address207000016 and cache disable at 407000016.When reading or writing to any of theseaddresses, DSACK0.1 are returned to termin-ate the cycle but data on the bus is irrelevant.

David Bums and David Jones are applica-tions engineers at Motorola's East Kilbrideplant.


-ThECOMMS TOPICSMonitoring theAtlantic Ocean

IntelsatIntelsat has awarded a contractto Mercury Communications Ltdfor the monitoring of IBS trans-ponder usage on one of its satel-lites.

It will monitor the I1/12G1-1zbeam received in Europe fromthe Atlantic Ocean Intelsat Vsatellite and forward the dataobtained to Intelsat's Washing-ton headquarters. The major ser-vice carried on this satellite is theIntelsat Business Service (IBS)which is a totally integrateddigital service allowing carriersto offer voice, data, facsimile andvideo transmission. Mercury isthe largest user in the world ofIBS and its parent company,Cable and Wireless. is the largestoperator of international com-munications satellite earth sta-tion,- in tlir Intrls,it systcm.

Toshiba to enterUK telecoms

marketAs part of its expansion plans,Toshiba has announced that it isto enter the UK telecommunica-tions market. It will he laun-ching Group 3 (sub 1 -minute)facsimile machines and hopes toreceive approval in the Autumnto sell the first of its small keytelephone systems in the UK.

When announcing his corn-pany's entry into the UK businessfacsimile and key telephone mar-ket. Mr Shunki Yatsunami,chairman of Toshiba Informa-tion Systems (UK) Ltd. forecast aturnover of £100 million($150m) by 1990 for its full rangeof office automation products.

Home bankingnetwork forAustralia

Two UK companies are to supplytheir products to the giant West-pac bank in Australia to enable itto provide its customers with fullhome and office banking facili-ties. Known as Handyline. theservice allows Westpac's custom-ers to transfer funds, pay credit

The Royal National Lifeboat In-stitution (RNLI) is to replace itstraditional call out devices,such as explosive flares, withradiopagers. British TelecomMobile Communications hasdevised a suitable system andis supplying 2000 specially

adapted radiopagers over thenext two years. The first hatchof 1000 is being delivered tolifeboat stations which are, atpresent, hampered by poorcommunications or cumber-some call out procedures.

cards, obtain a statement and thebalances in their accounts usinga digitized voice delivery service.

The complete 132 -port net-work incorporatesVideogate network concentra-tors and Langston's P111 soft-ware. and has been supplied bytheir Australian agents. ThornEMI Information Technology.

World record565Mbit/s opto

linkTelephone Cables Ltd (ICU hasinstalled, on behalf of MercuryCommunications Ltd. what is

claimed to be the longest, oper-ational. unrepeatered. single -mode optical -fibre network inthe world, working at 565Mbit/sand 1300nm using standard pro-duction fibre.

TCL installed the 10 -fibre toprovide a 51km two-way linkfrom Wolverton to Mercury'sWhitehall Satellite Earth Sta-tion, via Bicester in Oxfordshire.Even though it was expected toneed a repeater at its midpoint.attenuation test results sug-gested that this would not benecessary. As Mercury wished tooperate the cable at 565Mbit/s.further tests were carried outwhich provided necessary con-firmation.

Not only has this assisted Mer-cury on this route by avoiding

the need for a repeater site, it isnow possible that most futureroutes can be planned withoutthe need for repeaters, thus re-

and increasing re-liability.

Renaultsby packetswitching

Renault. the French state-ownedcar company, is to extend itsDirect Vehicle Ordering System(DVOS) throughout Europe. Thesystem. developed in Paris by thecompany itself, has been servingthe company's French dealernetwork for the past two years.Now. at a cost in excess of I

million, the 300 Renault dealersin the UK have gone on thesystem which will now also betaken up in Germany. Italy andother European territories.

The total investment by Re-nault in DVOS runs into severalmillion pounds so far. This in-cludes two Amdahl mainframesin Paris and a Tandem computerin London. Major connectionsare made via X.25 packet -switched networks - Transpac inFrance and British Telecom'sPSS in the UK.

In Britain. it represents justthe first phase of extensive com-putet ized communicationsbeing built into the company'sUK operations during the next

two or three years. aimed atputting the Renault network intothe forefront of communicationsadvances being made in the auto-motive industry over the comingdecade.

Small -dishsatellite trials

Trials of a small -dish satellitebusiness communications ser-vice were started by British Tele-com in May. The service willallow users at terminals at manydistant locations in Europe as%veil as the UK to exchange dataeasily and cheaply by satellitewith their company's centralcomputers.

The trial service is based onthe Very Small Aperture Termin-als (VSATs) and uses dish anten-nas of 1.2m (4ft) or 1.8m (6ft)diameter installed on customerpremises. It will enable links tobe set up quickly, even whenterminals are moved to new loca-tions.

It is centred on BT's LondonTeleport, its central satellitecommunications earth station inLondon's dockland, whereequipment from Comsat Tech-nology Products has been instal-led to act as the network hub forthe service. Any remote site maycommunicate with the hub, or toany other VSAT via the hub.

Applications to be evaluatedduring the six months trial in-clude the distribution of newsand images for information ser-vices. internal company electro-nic mail and other interactivecorporate data communications.

First all-optolaser amplifier

repeaterThe first field trial of a laseramplifier repeater has been suc-cessfully carried out in a 120kmfibre link installed in the BritishTelecom network. All optical sys-tems. when developed commer-cially. promise considerable sav-ings in the cost of optical com-munications links. especially forundersea systems. By avoidingthe need to convert the opticalsignal to an electrical one andthen back to light. they will besignificantly cheaper and moresimple to make. and their power


jttECOMNIS TOPICSrequirements will he reduced.

Still in the experimental stage.it is the optical equivalent of thetravelling -wave tube used as amicrowave amplifier. When heldbelow threshold, it emits an am-plified light pulse at one end inresponse to an incoming triggerpulse at the other.

It has been further demon-strated in the laboratory that.using wavelength -division mul-tiplexing. it can simultaneouslysimplify separate sets of pulses atdifferent light frequencies. It canalso amplify such pulses whenthey are travelling in the devicein opposite directions at once.These lab. tests were carried outover 50km of fibre withwavelengths of 1525 and1506nm and data rates of 280and 565Mbit/s. The light sourceswere distributed feedback laserswhile. at the receiving end of thesystem. channel filtering wasachieved using fixed -wavelengthinterference filters.

The amplifier is a laser. mod-ified by having its end facescoated to reduce their reflectivity500 times, thus destroying thelasing action. A steady voltage issuperimposed between the upperand lower surfaces to establishan electric field across the cavity.As a result, when a pulse of lightenters the cavity at one end, itstimulates the production of ex-tra photons which leave the cav-ity at the far end.

Expansion insecond phone

serviceResidential customers and smallbusinesses in the Nottinghamand Derby areas will take part intest marketing of the new Mer-cury 2300 telephone service. Inaddition, the company has ex-tended its local call services forits directly connected customersin the Birmingham and Man-chester areas.

The two Midlands cities arekey locations in the Mercury"Figure of Eight" network, andhave been selected to gauge theimpact of the service with re-sidential and smaller businesses.It will offer cost savings averag-ing 15 per cent on long-distancecalls, and up to 10 per cent onselected international routes in-cluding USA. Canada, HongKong and Bermuda. Mercury

will monitor the trial closely.carefully evaluating customerreaction and the degree of take-up as part of its plans for anationwide service to completewith British Telecom.

To use the new service, cus-tomers will need to purchase aspecial Mercury Telephone at acost of £51.99 (inc. vat) and payan annual fee of £8.62 (again inc.vat) for an Authorisation Code.Calls are made using the custom-er's existing exchange line sothat, to place a Mercury con-nected call, the trunk or interna-tional call is dialled in the usualmanner except that, prior tocommencing dialling, the M(Mercury) button on the phonemust be pressed.

The local call service, whichwill be most beneficial to thosecompanies with more than 30exchange lines, was previouslyonly available to directly con-nected customers in London. Itwill enable business customersto make savings of up to 30 percent on local calls.

Fax expansionfor BritishTelecom

With facsimile growing at anaverage of 100 per cent each yearfor the past six years and fore-casts suggest that next year afurther 75,000 terminals will beadded to the 90,000 currently inoperation. British Telecom hasadded two new machines to itsrange. They are a personal com-puter based machine providingstore and forward features for

fax, linked with test processingfor the high volume user andcompact, low-cost, desk -topmachine incorporating an integ-ral feature phone. The former,the MerlinFax PC100 providesthe user with an icon -basedmenu display for ease of opera-tion. At each stage, help informa-tion is available on request toguide the inexperienced user.

The latter, the HS20, is a jointproduct of British Telecom andTeleverket, the Swedish PTT,and has already been launchedon the Swedish market. Lookingrather like a sophisticated fea-ture phone it is claimed to in-corporate sufficient features tosat isfc mast users.

Prudentialapproach to

telecom-munications

Prudential Corporation, the in-surance and financial servicesgroup. has taken delivery of theone -millionth line of Plessey'sISDX digital p.a.b.xs as part ofthe process of implementing oneof the country's largest and mostsophisticated private digital net-works. Based on ISDXs of varioussizes it will extend from Scotlandto the West Country.

To date, the number of exten-sions at Prudential's five Londonand Reading head office estab-lishments and another selectednine offices around the countryis 4.250 in the network featuringthe latest d.p.n.s.s. (digital pri-vate network signalling system)

technology. This allows manyfeatures such as call diversionand call-back when free to beavailable between offices. Inaddition. Direct Dialling In(DDI I routes an incoming calldirectly to the called internalextension. At the present time.the company's 24 regional officesare being equipped with smallerISDX-SN exchanges on a stand-alone basis. In due course, whenthis replacement programme iscompleted. they will he con-nected to create one of thelargest and most sophisticatedprivate digital telephone net-works.

Since being launched as theIDX (Integrated Digital Ex-change). and now offered withISDN features. Plessey has soldover 3.000 of these switchesworldwide and achieved a salesrevenue of around £250 million.

Packetswitching cutsbank security

costsLargest clearing bank. NationalWestminster. is to use its privateX.25 packet data communica-tions network to carry alarm datafrom branches all over the UK.This will enable it to dispensewith the central alarm monitor-ing stations of security companyChubb Alarms Ltd. Chuhh is re-sponsible for the security of 350out of the banks 2000 branches.

Chubb engineers and NatWestd.p. experts worked together onthe system developed by Chubband already in use by two otherEuropean banks.

Under the programme. bankbranches are being equippedwith a specially developed inter-face unit which accepts signalsfrom intruder alarm systems andthe electronic security devicesprotecting Automatic TellerMachines (ATMs). When regular-ly polled by one of the sevencentral monitoring stationsaround the UK. an interface in-serts encrypted data packets intothe private network. Chubbclaims to have reduced thenecessary data traffic by 90 percent without sacrificing the levelof security.

Telecomms Topics is written byAdrian Morant.


RESEARCH NOTESIntensive carebiofeedback

What is probably the most soph-isticated biofeedback systemever invented has been developedby John Packer of the Depart-ment of Electrical and ElectronicEngineering at the University ofMelbourne. It's an automatic.computer -based device for stabi-lizing the blood pressure ofseriously ill patients. This is nor-mally achieved manually by reg-ulating the infusion of differentdrugs, a task that involves takingblood pressure readings usuallyevery 30 seconds.

An obvious electric alternativewould be to have a continuousblood -pressure sensor and con-nect it to a dispenser for twodrugs, one to increase bloodpressure and one to lower it. Thiswould in theory eliminate anyneed for manual intervention bynurses. It isn't as simple as that.however.

Mr Packer says that there areseveral reasons why researchersin Britain, the USA and Australiahave found difficulty in im-plementing such a biofeedbacksystem for blood pressure con-trol. One is noise from the bloodpressure transducer caused bymovement or by coughing:another is the variation inpatients' response to a drug atdifferent blood pressure levels.

These problems have nowbeen taken care of by the de-velopment of a computer prog-ram that can distinguish signifi-cant changes and convert theminto an appropriate response.The system adapts to variationsin patient sensitivity andincorporates a wide range of safe-ty alarms. Patient data is display-ed graphically on a v.d.u. andstored on disc for subsequentanalysis by medical staff. Doctorsand nurses can interact with theprogram through a standardkeyboard.

Clinical trials involving morethan 80 patients have been suc-cessfully carried out in intensivecare and cardiac surgical units.

How the brainis wired

Speculation about how the hu-man brain works has been apreoccupation since time im-

memorial and never more sosince the advent of the compu-ter. But whilst nerve cells orneurons behave in some wayslike silicon switching elements.the similarities are in other waysquite limited. The switching rateof a neuron is, for example.thousands of times less than thatof a typical c-mos gate. Neuronalarchitecture is also markedlydifferent from that pioneered byvon Neumann, being massivelyparallel. But of course, it isn'tquite as simple as that or wewould already be well on the wayto suitcase -sized computers withhuman intelligence and con-suming only a few tens of watts ofpower.

One of the most puzzlingaspects of the brain is how itwires itself up in the first placeduring foetal development.Obviously hidden away in thegenes there must be a sort ofwiring diagram written inmolecular code. But it can't bejust like a computer circuit dia-gram because there simply isn'tenough space on the genes for allthe data. This has led molecularresearchers to speculate that thebrain must in some way 'selfwire' itself.

Dr Adrian Aitken of the Uni-versity of New South Wales hasnow provided a little more evi-dence that this is exactly whatdoes happen. His first achieve-ment was to make a preparationof an intact foetal rat brain with-out disturbing the structure.Hitherto brain researchers haverelied on making microscopeslides from thin slices of tissue.In computer terms. Dr Aitkenhas discovered how to take thelid off whilst others are attackingthe innards with a chain saw.

Having got inside the foetalbrain, the next step was to followthe growth of the neuronal ax-ons, the links or wires by whichneurons connect themselvesinto the circuit matrix. The pre-cise method employed was de-tailed and complex but it led DrAitken to some fascinating andsignificant conclusions.

Neurons, it seems, have mole-cules that cause the growingaxons to follow a sticky trail inthe brain tissue. It's as if the pinof an i.c. were to sniff outanother i.c. and begin growing awire link. Dr Aitken says that the'stickiness' of the top of a grow-ing nerve fibre governs the direc-tion in which it \ill grow. In this

way the nerves do not necessarilyhave to 'know' which other cellsof the developing brain to con-nect to. All they have to do isfollow the adhesive trail.

These findings, recently pre-sented in a paper to the Austra-lian and New Zealand Society forCell Biology are significanttheoretically and also clinically.In future research. Dr Aitkenintends to examine more closelythe mechanism of nerve -fibreguidance and he hopes that, withadditional information. it may bepossible to direct the growth ofnerve fibres and ultimately de-termine their networkarchitecture. This has applica-tion in the treatment of severalnerves and also in the under-standing of degenerative neuro-logical conditions such as multi-ple sclerosis and Parkinson's Dis-ease. Conceivably it might alsofacilitate brain transplants!

Unmaskedchips

Implanting dopants directly intoa silicon substrate is an attractiveproposition for the manufactureof v.I.s.i microcircuits. Apartfrom avoiding the need for amask such a technique wouldpermit variations, either in thelocation or degree of doping.

A research programme involv-ing Manchester University. theUniversity of Manchester Insti-tute of Science and Technology(UMIST) and IBT-Dubilier is cur-rently looking at practical waysof implementing the Cu. ham-Dubilier liquid metal ion source,

Dopant ions

I Accelerator

Liquid metal(reservoir

Needle=

shown in the diagram. The ionsource consists of a positively -charged needle of less than10p.m diameter placed near anion accelerator electrode. Liquiddopant is fed by capillary actionfrom a reservoir behind theneedle and is then emitted as abeam. Focussing is achieved byelectrostatic or electromagneticlenses.

For the system to work prop-erly, the dopant material mustmeet certain tight constraints. Itmust flow over the needle with-out dissolving it. It must alsohave a suitable low vapour press-ure. Unfortunately neither arse-nic nor boron, the most commondopants. meet these criteria.

What the group have found isthat certain alloys of the dopantsdo meet the criteria and thatonce the alloy has been ionized,the unwanted component can beseparated by a technique analo-gous to mass spectroscopy. (Re-member the ion traps on oldcathode ray tubes?)

Where arsenic is concerned.an alloying material that workswell is platinum together with atungsten needle. With boron,platinum is also employedthough rhenium is the preferredneedle material. Computer stu-dies are now going on at Man-chester University to try and findthree -component alloys that per-form even better.

Flying powerstation

A new slant on power generationis a flying windmill being de-veloped by Associate ProfessorBryan Roberts at the Universityof Sydney. The Gyromill, as it'scalled, is a cross between a wind-mill and an autogyro and fliestethered by steel cables to theground. These cables not onlyprovide anchorage but also con-tain power cables and controlcircuits for ground commandsignals.

If the whole idea of putting apower station in the sky seems alittle eccentric. ProfessorRoberts explains that there aretwo major advantages from thisapproach compared to the use ofground based windmills. Con-ventional windmills of the sortnow springing up around theshores of Britain are so close tothe ground that the wind is bothslower moving and more turbu-lent than higher in the atmos-phere. Since the extractablepower is related to the cube ofthe windspeed. the advantages ofa few extra mile/h are obvious.Turbulence is a different andaltogether more serious problemand has led to at least one wind-mill in the USA breaking upcompletely. If you doubt the im-


RESEARCH NOTESpact of turbulence on largestructures near the ground, justrecall how bumpy it gets as anaircraft is landing.

The Gyromill prototype hastwo contra -rotating blades, each4 metres in diameter and eachdriving a 3kW generator. Profes-sor Roberts has already done thesums to show that this can easilybe scaled up to several mega-watts at least. Tests on the pro-totype have also shown thatthere are no serious problems.

When the windspeed exceedsabout 25km/h, the Cyromill willtake off from the ground andhover like a kite, generating elec-tricity as it does so. If the wind -

speed near the ground isn't quitestrong enough for an unassistedtake -off, then the generators canhe employed in reverse as motorsuntil the Cyromill is airborne.The motors then revert to theirnormal role as generators.

The mechanics of the machineare extremely complex, to ensurethat it will fly stably in all windconditions up to gale force. If thewind does become dangerouslygusty, then the Cyromill canadjust its blades so as to landsafely and switch off. ProfessorRoberts hopes eventually tobuild a fully automatic versionthat will take off and land underfull computer control. The com-puter would respond not only tothe prevailing wind conditionsbut also to the needs of theelectricity utility. Gyromillscould be kept on the ground andthen launched automatically atperiods of peak demand.

At the moment, flying power -stations on this grand scale maybe a little way off, even in Austra-lia. But Professor Roberts be-lieves that the idea may haveimmediate applications in areaslike Antarctica where the prob-lem of ground turbulence is ex-acerbated by icing and wherediesel generators pose difficul-ties of their own. Flying at about300 metres above the icy waters,a Cyromill would be fed by asteady stream of air, largely freefrom drifting snow.

Major researchgrants forantennas

Over the past few years theAntennas Group in the Electro-nic Laboratory at the Universityof Kent has been awarded sub-stantial research grants from theScience and Engineering Re-search Council and BritishAerospace for work on satelliteantenna systems. Recently thegroup has received two furthergrants, from the SERC and theRoyal Signals and Radar Estab-lishment, each of more than1100,000. The work of thegroup, surpervised by Dr TedParker, Reader in Radio Com-munications, and Dr R.J. Lang-ley, Lecturer in Electronic En-gineering, is concerned with stu-dies of frequency -selective sur-faces.

These can be used to constructcomponent parts ('subreflec-tors') of communications anten-nas. which can then becomecapable of operating on severalwavebands simultaneously,thereby improving the efficiencyand cost effectiveness of the sys-tem. In some of these applica-tions, the surfaces have to bequite tightly curved, and theaims of the project funded byRSRE are to improve the designprocedures for curved surfacesand to develop manufacturingtechniques.

In other applications, two ormore surfaces are stackedtogether in cascade, or the sub -reflectors have partly metallicand partly frequency selectivesurfaces. The grant from SERC issupporting a study of these morecomplex structures.

Electrolumine-scent blues

A paper published jointly by ateam of applied physicists atDurham University and a groupof chemists from UMIST de-scribes what they claim is thefirst ever room -temperature blueluminescent device based onmetal -insulator -semiconductor(m-i-s) technology. This offersan alternative configuration tothe more common p -n junctionused in opto-electronic devices.

The latest m-i-s diode employs

Gold

Silicon phthalocyanine

ZnSe

GaAs

Indium

0

zinc selenide (ZnSe) as a 11 -VIsemiconductor. This is on a gal-lium arsenide substrate fabrica-tion using metal organic che-mical vapour deposition(m.o.c.v.d.) at room tempera-ture.

The 'insulator' part of the m -i-s structure is a Langmuir-Blodgett (molecular thickness)film made of a silicon phthalocy-anine compound. At an appliedvoltage of around 2V, a current ofapproximately lmA flows; this isthought to be limited by theinternal resistance of the siliconphthalocyanine layer. Undersuch conditions the researchersreport a blue -white emissionfrom beneath the gold contactlayer. Such light is said to beclearly visible under normal in-door lumination.

Further research is now inprogress to establish the opti-mum thickness of the 'insulator'layer.

Magnetohydro-dynamics to

beat pollutionA research team at the Universityof Sydney has developed a prac-tical means of improving theefficiency of existing coal-firedpower stations, using a novelmagnetohydrodynamic conver-ter. Magnetohydrodynamics isthe process whereby hot gasesfrom the burning fuel can heused to generate electricitydirectly.

In essence, the m.h.d. gener-ator works by taking the hotgases and ionizing them with aseed material to make them elec-trically conducting. The gasesthen pass through a magneticfield in which charge separationoccurs, resulting in a currentflow between pairs of collectorplates and an external circuit.

The Sydney m.h.d. generatordiffers from the usual approachof feeding the gases along astraight channel; instead it em-

ploys a disc structure in whichthe flow is radial. This makes thesystem more compact and en-ables it to produce much morepower per unit volume thanlinear designs. It is also substan-tially cheaper because the mag-net used is simpler in design.Where the researchers, led by DrSteve Simpson, have made sub-stantial advances is in the de-velopment of insulating mate-rials capable of withstandingtemperatures of around 2000°C.

The disc m.h.d. generator, oneof only three of its kind in theworld, has now been runningsuccessfully for almost a year atWhite Bay power station in NewSouth Wales. Tests show that it isperforming beyond expectations.The team is particularly pleasedwith the generator because theyclaim that the other two discm.h.d. generators at StanfordUniversity in the USA have notproduced such encouraging re-sults. Also encouraging are theresults of a computer studywhich predicts that it should bepossible to scale the design up.

Although m.h.d. is still in itsinfancy in terms of development.many countries are now lookingat the technology as a means ofreducing pollution and gettingmore electricity from a givenamount of fuel.

Electricity is generated

Ionizedgas

CoalcombustorExhaust power plant

I Steam

Where m.h.d. scores is that itmakes use of very high tempera-tures at which conversion effi-ciency is high. And because theexhaust gases are still extremelyhot by normal standards they canbe re -used to boil up water anddrive a turbine in the conven-tional way. The most practicalway of employing an m.h.d.machine is therefore as a sort of'front end' to an existing station.But whether extensive use ofm.h.d. would improve efficiencyto the point where coal-firedpower stations are as competitiveand free from acid rain as nuclearstations remains to he seen.

\otsv tie\6

Disc channel

Research Notes is written byJohn Wilson.

73i ELECTRONICS & WIRELESS WORLD

Minimal epromprogrammer

Special protocols devised to suit last month's hardwareallow software to take over all the tasks in reading or

writing eproms.

The simple hardware described in theJune article can be controlled by anycomputer with a serial interface cap-

able of communicating at 9600 baud. Creat-ing the necessary software is not an enor-mous task, but is made vastly easier by thehelp of a high-level language such as Basic,Pascal, or C. Most of the procedures neededare available from such languages, with theexception of a few low-level functions whichmay require either machine code or systemcalls depending on the operating system inuse. I have used the C language to imple-ment the procedures for two different com-puters and three different operating systemsand found the source code was portable in allcases with only the need for a few differentassembly language routines to be bound inat link time.

Features of the program break down intothree classes: the necessary, the fairly essen-tially useful, and the nice. Necessary are thefeatures required to write and read epromsfrom and to disc files. The useful features addthe capacity to display eprom contents, toverify eprom contents against files and todisplay informative screens and warningmessages. The nice features may includeprovision of progress reports during pro-gramming, verifying and copying, dif-ferentiation during verification between re -programmable and erasure -requiring faults.and file name and file size buffers to elimin-ate the need to retype the file identification ifmultiple copying and/or verification is re-quired.

The necessary features are built from thefollowing software functions:1. initialize serial communication to 9600baud, no parity, two stop bits. eight data bits:2. open a disc file for reading or writing, andclose it again:3. flush the computer's and/or uart's serialreceive buffer:4. output an eight -bit character through theerial port with no handshake:

5. wait for an eight -bit character to arrivethrough the serial port, input it, with nohandshake:6. do nothing for 50 milliseconds (± 5ms).

Some of these functions may not requireprogramming: for example, on my CP/Mmachine dip switches set up the serial portparameters. Some functions may come aspart of your language, and some may requiremachine code or assembly language pro-gramming.

13.J. SOKOL

Table 1. Hardware settings for different communica-tion parameters (uart type 6402, 8017 8502 etc.)

Pin High Low

35 No parity Parity enabled36 Two stop bits One stop bit39 Even parity Odd parity

A detailed discussion of these functionswill follow, but first let us assume they areprovided, and consider the program fromthe top down. The two essential functions ofthe eprom maker are transfer of rom con-tents to and from disc files. These use thefollowing program flows.

For reading: initialize. flush the buffer,open a disc file to read into, then repeat thefollowing as many times as there are bytes tobe read:

send a dummy byte (say. 0).input a byte and store it as next in the

file,send another clib Imy byte,input a byte and discard it.

After all bytes are read close the input file.For writing: initialize, flush the buffer,

open a disc file to write from, then repeat thefollowing as many times as there are bytes towrite:

fetch the first/next byte from the fileand output it,

unless the fetched byte is FF1h. delay50ms

input a byte and discard it,output the fetched byte again.input a byte and discard it.

Finally inform the user writing is done andclose the output file.

CREATING PROCEDURES

If serial communication parameters are notavailable as listed above you may use differ-ent parameters and change the hardware inaccordance with Table 1, perhaps with moredividers after the 4520 in the bit -rate gener-ator.

Opening and closing disc files are tune -


tions of any high-level language, and withmost you can use buffered file i/o to saveconsiderable execution time.

If a serial communication flush functionis not provided it can be implemented by asoftware loop that repeats as long as there isa byte to be read from the serial port -reading in a byte, discarding it, and tryingagain.

Outputting and inputting with no hand-shake may require an interface directly tothe hardware of your uart, as operatingsystem calls (for example under MS-DOS)may scan Dm or other signals before sendingor receiving serial bytes. The (not recom-mended) alternative to taking the troublewith software is to wire up a special DB25serial plug involving pins 4,5,6 and/or 20 andperhaps others with the right combinationof shorting links.

On a simple computer, like my CP/Mmachine, the delay procedure is im-plemented by simply entering a loop tocount up to a constant number, uselessly.This is not practical with IBM p.c.-typemachines for several reasons. One is thatprocessor speeds vary greatly. Somemachines use two or even three differentprocessor speeds selectable by the user, andsome turbos don't even have the standard4.77MHz as one of their options. Added tothis is the difficulty that the various mem-bers of the Intel and NEC families of proces-sor used in p.c.s queue instruction in aninternal pipeline in differing ways, so thatthe time required to run a delay loop is notproportional to processor speed from onemachine to another. Finally, a p.c. runningDOS is not strictly a single thread machine,for the foreground task is stopped at inter-vals to allow d -ram refresh and for a systemclock interrupt which may be trapped bymemory -resident software.

The solution to these problems is to let thesoftware figure out the delay parameters foritself. As in the simple case, a delay loopcounter is used, but the counter goes up to avariable limit rather than a constant one,and the variable is adjusted each time theprogram is entered.

The assembler and C functions given inTable 2 show how this can be done. Thedelay(n) function is tested 50 times by theadjust( ) function using an initial value for nwhich is about right to produce a 50ms delayon an XT using a 4.77MHz clock. DOSsystem calls 2Ch and 2Dh to set and read thetime are bound in using assembler routineszerosec( 1 and readsec( 1. These allow thenumber of seconds elapsed during the 50in -line iterations of delay(n) to be measured.The resolution of these system calls isworse than 50ms, but repetition of the delaymeans the timing of each delay call ismeasured to about ± lms, five times asaccurate as is required for eprom program-ming.

Table 2 shows how time informationobtained from readsec( ) can be re -formattedto an integer from the mixed binary anddecimal format supplied by DOS (the highbyte of the data word is seconds, the low byteis hundredths of seconds), then cast into afloating point form, and then divided intothe expected number of 2.5 seconds to

Table 2. Two C and two assembler functions to adjust the delay function del(newfac) to 50ms Functionszerosec and readsec should be declared -public. assembled and then linked to the C program.

delay( timer)int timer;

int n;for ( n=1; n< = timer ; n++) ;

adjust()

int timer,readsec(),factor,timfac,newfac;float correct,timff;factor=2200;

zerosec(); /*zeroes seconds, leaves minutes

delay (factor);delay (factor);delay (factor);

and etc to fifty times

timer= readsec();/*returns sec in hi byte, hundreths

timfac=(100*(timer/256) + (timer&Oxff));/*corrects this to an integer*/

timff=timfac;/*casts this to a float*/

correct = (250/timff);newfac = (correct * 2200.0);

printf ("The speed factorreturn (newfac);

rosec : pushpushpushmovintmovmovintpopspoppopret

bpdxcxah,2ch21h ;read timedx,0 ;zero secsah,2dh21h ;set timecx -

dxbpageomilliaL

& hours*/

in lo byte*/

of your PC is %f.\n",correct);

readsec_: push bppush dxpush cxmov ah,2chint 21hmov ax,dxpop cxpop dxpop bpret

obtain a correction factor for the originalguess at the delay constant. A correctedconstant is then returned to the calling mainprogam for use in the 50ms delay loop whenrequired. The entire process takes 2.5seconds at most, and (for the sake of simpli-city) resets the seconds counter of thesystem clock once to cause a 'loss' of at most59 seconds.

Now we turn to useful aspects of thesoftware. Menu screens can be designed tocontrol of the various modes of operation. Itis also useful to add a mode to display thecontents of an eprom while they are beingcopied to a disc file.

A verify function is very helpful. It readssequential bytes from the eprom but opens afile for reading rather than writing, andcompares the eprom contents with sequen-tial bytes from the file and displays anydifferences found.

The first of the nice functions memorizesthe identity and size of the last file used toallow the re -use of the same data. Thisfeature has certainly saved me enough in'time and temper (and typing errors) to havemade the tussle with string processing in itsimplementation worthwhile.

Another function puts blobs on the screenin blocks indicating 1Kbyte processed, togive a progress report. One blob per 64 bytesgives just enough information during pro-gramming to give comfort that something ishappening without wasting too much timedoing screen writes. It is also useful that the

number of bytes to be programmed can beselected to be less than the full epromlength, allowing partial programming wherethis is suitable. To program the popular 2764eprom fully takes eight minutes (less if thereare 'blank' areas with FFs in them). A 27256can take half an hour to program.

A final nice feature is an addition to theverify function that reports whether epromerasure is required when there is a mismatchbetween a file and the eprom contents.Erasure is required when an eprom bit is lowthat should be high. The software reportseach such mismatch with a message and anaudible signal. This makes checking thesuitability of an eprom for overwritingwith agiven file a matter of listening rather thancareful watching. Silence during the verifyfunction means overwriting is possible be-cause all mismatched bits are high.

The author can supply executable soft-ware, a brief manual on disc, and a programuseful for comparing two binary files. Thebasic version is available for a Morrow MD2or MD3 CP/M system, or a Morrow with SWPcoprocessor under CP/M86 or PC -DOS for£10 plus s.a.e. disc mailer froth B.J. Sokol,47 Grafton Road, London NW5 3DX. Thefully featured program as described here isavailable for PC compatibles with a COM1:serial port for £15 plus mailer.Jerry Sokol started his design consultancyin the U.S. in the early 1960s. He alsolectures in renaissance literature at LondonUniversity.


[SATELLITE SYSTEMS r -More out of

MACA new way of getting more tele-vision signals through a givensatellite transponder bandwidthfor tv signal distribution or d.b.s.has won an international prizefor a British researcher. CalledD-SMAC, the system is the workof W.H. Dobbie of British Tele-com Research Laboratories,Martlesham Heath, Suffolk. MrDobbie has won the $10,000Piero Fanti international prizefor 1986 given by the Italiancompany Societa TelespazioS.p.A. It honours the late DrPiero Fanti, who was Telespa-zio's first director general, and isawarded to the winner of a com-petition open to all students andresearchers in countries whichare members of INTELSAT. Theprize was presented at a

Washington, DC meeting of IN-TELSAT signatories in April thisyear.

The new D-SMAC systemallows four tv signals to be car-ried by a 36MHz transponderchannel, compared with the cur-rent maximum of two signalsusing the PAL standard. It is

based on the existing D2 -MACsystem which has already beenproposed for d.b.s. and cable tv inEurope. In the name D-SMAC,the 'D' indicates that data is

multiplexed with the video signalat baseband, the 'MAC' is theaccepted abbreviation for multi-plexed analogue components,while the 'S' means that theseanalogue components are sub -sampled.

Basically the four tv signalsare transmitted through a36MHz transponder by frequen-cy division multiplex (f.d.m.) -that is, one tv signal in 9MHz.The techniques used to achievegood bandwidth efficiency in-clude a non-linear pre- and post -filtering process, the sub -sampling mentioned above (cal-led modified quincunx sub -sampling) and a method of adap-tive interpolation which allowsfor practical analogue transmis-sion. The system uses samples inthe current tv field for interpola-tion and so avoids an immediaterequirement for frame delay/stores and motion information.

Apart from signal distribution,Mr Dobbie's prizewinning paperstates that the same techniquecould be used in d.b.s. to allow a

This antenna at British Telecom International's Goonhilly earth station,Cornwall, is to be used for the BTI Skyphone service -a satcom schemeallowing air travellers to make in-flight telephone calls from aeroplanes.The scheme follows from INMARSAT's 1985 decision to offer aeronautic-al mobile satcom services through its L -band maritime satellite network(January issue, p. 32). BTI Skyphone is one commercial system set up toexploit this new form of public telecommunications and will operateinitially on transatlantic routes through INMARSAT's Atlantic Oceansatellite (MARECS B2) at 26° W. International direct dialling will bepossible for passengers. Voice signals will be digitally encoded, initially at9.6kbit/s, and data transmission will be available through the system,initially at 600bit/s. Standard airborne equipment will have up to fourtelephone channels per aircraft (four simultaneous calls). Avionicsmanufacturers are at the moment considering wall -mounting cordlessunits and integral seat -back units. Eventually the BTI Skyphone servicecould be extended to work through the INMARSAT comsats over theIndian and Pacific Oceans.

doubling of broadcasting capac-ity "without significant loss ofquality compared with PAL inthe short term, with the optionof trading the increased capacityin a compatible manner for en-hanced definition and aspectratio in the future." The sub -sampling method "allows the en-hancement information to beoverlaid in an effective and sim-ple manner."

Mr Dobbie works in a groupconcerned with terrestrial inter-faces and baseband processingwithin the Radio and SatelliteCommunications Division atMartlesham. This outfit is nowbuilding a prototype codec basedon the D-SMAC principle. It willbe used for signal distributiontrials over a typical satellite linkprobably later this year, to in-clude subjective comparisonswith current distribution sys-tems.

Advancedcommunication

throughOlympus

Digital television, high -definition tv, telecommunica-tions to aircraft. adaptive chan-nel coding, correlative phasemodulation, simulated on -boardprocessing and countermeasuresagainst fading are among themany advanced radiocommu-nication experiments booked forthe ESA Olympus satellite after itis launched next year.

This large multi -purpose com-sat, weighing about 1.5 tonnesand measuring 26 metres fromtip to tip of its solar arrays, isreally an orbiting test-bed foranything that the EuropeanSpace Agency and other orga-

nizations may want to try out forthe future. In geostationary orbitat 19° W, the first flight modelwill carry four distinct payloads.One is for direct broadcastingprojects, another is for special-ized services (such as education,newsgathering, business), athird is for advanced com-munications experiments at 30/20GHz, while the fourth is forpropagation studies.

At a recent lEE colloquium on'Satellite communications above18GHz' an overall picture of theexpected utilization of thesepayloads was given by C.D.Hughes of ESA, Noordwijk,Netherlands. Probably of mostinterest to E&WW readers is theintended advanced communica-tions work at 30/20GHz - whichof course is on the verge of themillimetre -wave region. Thepayload for this comprises three30W t.w.t. transmitters and twoindependently steerable spotbeams with a beamwidth (to the3dB contours) of 1°. The e.i.r.p.at beam centre is about 54dBW,allowing the use of small dia-meter antennas for earth sta-tions.

Altogether this payload pro-vides one wideband channel of700MHz bandwidth and twonarrow -bank channels of 40MHzeach. Uplinks are at 30GHz anddownlinks at 20GHz.

ESA will use this payload fordata relay experiments. Thesewill be to and from the Eurecaorbiting scientific platform dueto be launched in 1989. Thislow -orbit vehicle will carry aninter -orbit communicationsmodule which will send and re-ceive signals to and from thegeostationary Olympus trans-ponders. Eureca will be trackedby the steerable antennas ofOlympus and the data originat-ing from the platform will betransmitted and received by anESA earth station in Europe.

In broadcasting, said Hughes,there is a plan to demonstratethe ability of Olympus to relayhigh -quality television picturesand sound from remote parts ofthe world to European locationsfor broadcasting. In particular.using the steerable spot beamsand ESA's air transportable earthstations, it will be possible torelay items of topical interestfrom, say, South America to astation in Europe, from wherethe Olympus d.b.s. payload canhe employed to distribute the


SATELLITE SYSTEMSprogrammes. The EuropeanBroadcasting Union has showninterest in doing high -definitiontv experiments using the 30/20GHz payload.

The wideband capability ofthis payload will be used to makemeasurements of phase correla-tion in very wide band transmis-sions at millimetre -wave fre-quencies. There will also be anumber of scientific experimentsconcerned with countermea-sures for fading. These will in-clude experiments with diversi-ty, both in frequency and space,and with digital techniques foralleviating the effects of fading.Most of the more general experi-ments, for example a BritishAerospace video conferencingproject, will investigate fadecountermeasures as a necessarypart of radiocommunications at30/20GHz.

Many of the planned experi-ments are in the field of businesscommunications using smallearth stations, continuedHughes. The Canadian Com-munications Research Centrewill set up an experimental net-work of stations for such busi-ness communications. It willalso investigate the potential ofon -board processing systems.using double -hop techniquesand equipment on the ground tosimulate a future satellite signalprocessor.

British Aerospace and the ESAare to run a business com-munications experiment in theUK involving data, voice andvideo conferencing. Initially theESA's TDS-6 earth stations willbe used for this experiment atthree UK locations. Telespazio,in collaboration with thePolitecnico di Milano and otherItalian organizations, have alsosaid they want to carry out busi-ness communications and tele-conferencing experiments.

In data transmission, a num-ber of European scientific orga-nizations including the Universi-ty of Graz (Austria), RutherfordAppleton Laboratory (UK) andCNUCE (Italy) will operate aninter -networking experiment.This will link together computernetworks in the various coun-tries to demonstrate the possibi-lities of high-speed operation ofsuch systems. A further experi-ment called CODE (CooperativeOlympus Data Experiment) hasbeen devised by an earth stationworking group consisting of rep-

resentatives from universitiesand sceintific establishments.This will involve linking togetherscientific and educational estab-lishments using very small aper-ture terminals (February issue,p. 160, on v.s.a.ts) throughoutEurope.

Also using near mm -wave fre-quencies is the Olympus payloadfor propagation studies men-tioned above. The general ideahere is that the satellite providesa platform for source of electro-magnetic radiation in space.These are in the form of beacontransmitters. Olympus carriesthree such transmitters, withfrequencies of 12, 20 and 30GHz.They are all linearly polarizedand accurately aligned with eachother in polarization.

The 20GHz beacon can beswitched by telecommand be-tween two orthogonal polariza-tions or made to switch automa-ticaly between polarizations at arate of about 1kHz. This featureallows accurate measurementsto be made of differential polar-ization. The 12GHz beacon has aglobal converage with a mini-mum e.i.r.p. within coverage of10 dBW. The 20 and 30GHzbeacons have European cover-age, each with a minimume.i.r.p. of 24dBW. They aremutually coherent, being de-rived from a single oscillatorsource within the satellite whichis duplicated to ensure long-term reliability.

These beacon transmissions,said Mr Hughes, not only allowabsolute measurements of atte-nuation and cross -polar effects at20 and 30GHz but also permitdirect comparison simul-taneously between 12-, 20- and30GHz phenomena. He felt thisto be very valuable because it willenable the considerable amountsof propagation data already col-lected at 12GHz to be scaled tothe higher frequencies.

Offshore multi-channelsatcoms

Winds in the North Sea oftenreach speeds of over 100 knots(185km/h), so the dishes of anysatellite earth terminals usedthere have to withstand heftywind loadings which can deflecttheir radiation beams away from

the satellite position. In a newoffshore terminal, claimed to bethe first multi -channel satellitesystem used in the UK section ofthe North Sea oilfields, this prob-lem is dealt with by sophisticatedposition -control servos whichrespond to the wind buffetings.

The new satcom terminal,built by Ferranti, is installed in afloating production vessel work-ing at the Balmoral oilfield,225km north-east of Aberdeen. Avery demanding specificationmeant that a radome could notbe used for protection. Toachieve the required pointingaccuracy of 0.05° for the antennatracking and pointing system inthe fierce wind conditions theantenna mount is made veryrugged and position -controlledby a servo system using multipleprocessors.

This system receives error sig-nals from two sources. Dynamicvariations are sensed by an atti-tude and heading reference unitwhile slow drifts are obtainedfrom a step -track pattern. Aninput to the step -track system isprovided by a receiver picking upsignals from a beacon on thesatellite. The two correctionsobtained through these detec-tion systems are combined andthen used to control the anten-na's azimuth and elevationmotor drives.

Overall the floating satcomterminal provides voice and datacommunications at Ku bandthrough the European ECS-2space segment to a British Tele-com shore station at Bridge ofDon, Aberdeen. Transmitter r.f.power is 250 watts. Multiplechannels are obtained by thes.c.p.c. (single channel per car-rier) transmission method, a sys-tem widely used in satcoms forsending a large number of differ-ent voice or data signals througha single transponder. Modula-tion is by companded f.m.

Ten voice channels are initial-ly available, with an option forexpansion to 25 channels with-out alteration to the equipment.Data is transmitted in 64Kbit/scircuits but with a Viterbi systemof coding which results in anactual transmission rate of about132Kbit/s. Considerable use ismade of voice digitizing and sta-tistical multiplexing to achievethe highest possible transmis-sion efficiency. Equipment re-dundancy is applied throughout.

It seems that the Balmoral

oilfield is a 'marginal' one fromthe business point of view, with aprospect of high recovery costsand small returns. Combinedwith the recent oil price drop,this makes a difficult situationfor the suppliers of communica-tions equipment, as the oil com-panies don't have much moneyto spare for capital investment atthe moment.

Internationalappointments

INTELSAT has elected His Excel-lency Susanta De Alwis, the SriLankan ambassador to the USA.as the new chairman of the inter-national cooperative. He is sup-ported by Juan Ciminari ofArgentina, who was elected vice-chairman at the same time. MrCiminari, who has a degree inelectronic engineering, hasworked for Motorola in Argen-tina and served as that country'sSecretary of Communications.

After the somewhat dramaticdismissal of its previous directorgeneral (and his deputy) follow-ing an audit, INTELSAT has nowappointed Dean Burch of theUSA to this important post for aterm of six years. A lawyer byprofession, Mr Burch has had 30years' experience in telecom-munications, including chair-manship of the FCC and lead-ership of the US delegation to the1985 WARC at Geneva.

Newly elected chairman of thecouncil of INMARSAT is a Britishcommunications engineer, GeoffHall. He is currently head ofsatellite systems (planning andpolicy) in British Telecom Inter-national. In 1966 Mr Hall was incharge of the early UK satcomservices operated through thecountry's first earth station atGoonhilly. Later he worked forthe Comsat Corporation in theUSA and was involved in theestablishment of the INTELSATorganization. After his return tothe UK, Mr Hall was given re-sponsibility for all BT earth sta-tions in this country.

He served as the INMARSATcouncil vice-chairman in 1986.Taking over this position now isHideo Nagata, director of thesatellite and radio communica-tions department of KokusaiDenshin Denwa of Japan.

Satellite Systems was written byTom Ivall.


Crossover distortion inclass B amplifiers

Detailed tests on three modes of amplifier operation, includinga non -switching class B type, using the same basic circuit

produce a few surprises.

Ever since the publication of my circuitideal I have received questions as towhat extent the circuit was an

improvement over the traditional arrangement. Nearly every question emphasized thesubjective sensation of distortion reductionachieved'.

At the time I had measured the circuitperformance and found that the circuitdefinitely posessed certain advantages tojustify publication, but enough data wascollected to give a precise answer (other than"come and listen for yourselves").

Now I can give some answers regardingelectrical performance and offer some hintson what can be perceived. There are stillunknowns however and further experimentsare encouraged to throw more light on thesubject.

MEASUREMENT TECHNIQUES

Historically, crossover distortion was thefirst distortion mechanism encountered intransistorized audio amplifiers ("transistorsound"). It was considerably reduced byemploying the now common bias technique'sand it is surprising how little attention it hasreceived in literature since. By the discoveryand explanation of other distortionmechanisms it eventually faded into thebackground until the famous feedback vsfeedforward error -correction debate.followed by the subjective evaluation debate.Although subjective evaluation wasrecognised to produce statistically unusableresults', there remained an impression thatnot everything could be measured tocorrelate with the descriptions of what hasbeen perceived by the "golden eared" ones.In fact there are many works that stress theoutput stage non-linearities as the majorsource of problems (refs 5.7.8.10.12).

Various methods have been developed toevaluate amplifier distortion. Most of themuse steady-state signals to aid analysis.Several forms of distortion, however, havetheir origin in conditions that are variable bydefinition ("What have sine waves to do withmusic?").

Having experimented with different

Sync in

V

E. MARGAN

Signal in

10

Amplifierunder test

Trigger Plot xTransiert

Signal recorde-

Datalab OL 905; X

X Y

Plotter

ionI See appendix In

Phase tuning

Sk

334 /

22p

5534

75011.

3k

Referenceamplifier

2k7

3000

22p

Erroramplifier

3300

Fig.1. The "subtraction" test set-up due to Baxandall can be used with both steady-stateand transient signals and does not require a precision reference.

methods I finally decided that the'subtraction' methods' could offer most inflexibility as it requires no precision signalreference and can be used with both steady-state and transient signals.

Fig. 1 shows the test circuit. while Fig. 2shows the experimental amplifier built toenable comparative measurements betweenstandard class A and class B circuits and thecircuit proposed' which will be referred to asclass NSB (non -switching Bl. The circuitshown in Fig. 2 has the advantage of usingthe same devices in all the three modes, thusenabling direct comparison of test results.The front-end was built around a 5534operational amplifier with open -loop gain of60dB. unity -gain compensated by 22pF. a20dB closed -loop gain. 40dB overallfeedback and 200kHz closed -loop roll -off.The experimental amplifier performance iscompared to another 5534 as its basicperformance was considered acceptable by

power amplifier standards. This amplifierhas also a high -frequency single -polenetwork which matches its high -frequencyroll -off and phase to the experimentalamplifier. The output signals of bothamplifiers are summed together by aresistive network. Being of opposite phase.the output signals are effectively subtracted.leaving only noise and distortion at thenulling point. A further 5534 is used toprevent nulling point loading by other testequipment and to amplify the error signal( x 10) to increase the level as required by theinput sensitivity of the test equipment.

Using a sine -wave generator at first to testthe class B performance it was noted that ifthe level of distortion was changed thehigh -frequency single -pole control had to bereadjusted to give minimum output fromthe subtraction amplifier (Fig. 31. Toinvestigate the pattern of the change thegenerator was replaced by the circuit shown


in Fig. 4, consisting of a square -wavegenerator driving two tunable band-passfilters both with independent Q -factoradjustment. At high Q settings the filtersproduce exponentially decaying sine wavessimulating a real -life transient (Fig. 5, toptrace). Such a signal offers the advantage oflooking simultaneously at both distortedand undistorted amplifier response andmake direct comparison.

By trying to get minimum output fromthe error amplifier it was noted that if thephase was nulled in the high signal levelregion where crossover spikes occured thereremained considerable phase error in thelow-level region where no switchingdistortion was being produced (Fig. 5,middle trace). And vice versa: if the phasewas nulled in the undistorted region a lot ofuncompensated phase error appeared.broken by the crossover spikes (Fig. 5.bottom trace). This means that only whenthe output signal amplitude falls below thelevel of transistor cut-off both amplitude andphase effects can be cancelled completely.Increasing quiescent current considerablyreduced both phase error and crossoverspikes, but they could not be entirelyeliminated until the quiescent current wasgreater than the peak output current(essentially class A operation).

The obvious explanation is that when theclass B output stage generates distortion thevoltage gain stage is having a hard job torebalance the error sensed by feedback, butit can only react with its own open -loop

Fig.2. The experimental amplifier circuitdiagram function in three modes, A, B andnon -switching B.

15V

bandwidth and gain7. Also, the outputimpedance, being not near -zero underdistortion conditions, forms an attenuator.together with the load which becomes partof the feedback loop. This is confirmed byFig. 6 which shows error increase undercapacitive load.

The degree and nature of distortion inclass B configuration was a real surprise forit was expected that high distortion wouldshow up at levels where the inactive outputdevice becomes unbiased and eventuallyreverse biased (Fig. 7, top trace). That is alsowhy it was expected that class NSB bias mode(Fig. 7, bottom trace) could be a bettersolution. In fact, in Fig. 8, where voltagesacross the output emitter resistances arerecorded, the distortion threshold is reached

when the output level falls below 100mV (on4 ohm load, 0.4 ohm emitter resistances and100 mA quiescent current).

It was also found that distortion falls asthe voltage gain stage bandwidth rises,which was expecteds. This throws a bit morelight to schemes of alternative frequencycompensation networks9 and local errorcorrection techniques19.11. While thosemethods reduce the errors considerably, theproposed circuit eliminates them inprinciple, enabling the overall feedback to bealways effective. Comparing the recordedclass B performance with class NSB recordedin Figs 9 & 10 shows the distortiongenerated with class NSB operation is veryclose to the noise floor. These figures are thesame as can be achieved with class A

Fig.3. Class Boperation: Outputsignal, top trace.2V/div. Errorsignal, middletrace, 10mV/div.Decreasingquiescent currentfrom 100 to 20mAincreasescrossover spikesand phase must bereadjusted.bottom trace,10mV/div.Recorded withresistive load.timebase 2ms fullscale.

11N

T

CI ND

Systems p

measurement I 'T

yin

4

3M

3k 30k

15V

BC 212

62

7k5

1

220

ILset

2k

SlA

BC287

BC 287

7k5

220

BC 182

BC 212

04

BC 286

68

04

S 04

e w 68

220

BC 287-"\AA.,

7k5.12F7 :5

BC 286 1k

BC182

62 S1B

BC 286

04

15V


operation. Such performance speaks foritself.

The proposed class NSB circuit has severaldistinct advantages over similar circuitspresented before''. First, it uses onlynegative feedback (in contrast to positive orcombined positive and negative in similarcircuits) to sense and prevent switching off(Fig. 7, bottom trace). Secondly, thequiescent current is sensed directly, thus nothermal feedback is needed to achievethermal stability. Third. thermal stability ofthe circuit does not rely mainly on highvalue of emitter degeneration resistance, sothose resistances can be made small (lessthan 0.1 ohm) and so improve outputimpedance linearity in dependance of outputcurrent.

2 Hzsquare

9e^

Pulsedelay

50kHzlow-pass

filter

5k Hzlow-pass

f! [ter

Fig.4. Test signal generator block diagram.

50 m\

Fig.5. With exponentially decaying sine wave both distorted andundistorted class B response can be compared simultaneously.Top trace: test amplifier output. 2V/div. Middle trace: phase nulledin distorted region shows uncompensated phase in undistorted

2V

4

50u re-

Fig.7. In class B operation the inactive output device becomesreverse biased: the output voltage is compared to the bias voltageunder quiescent condition and with input signal applied, toptraces. 2V/div. No such condition is allowed in class NSB operation,bottom traces, 2V/div. Resistive load, timebase 0.5ms full scale.

201. H

band-passfilter

0(decayadj I

HFamplitude

T(decayadj

2k Hzband-pass

filter

Outputamplifier

1.-L F amplitude

s-/-yn,out

Signalout

$

2V

4

50 mV

4

$

200mV

4

50 J)1 VV I 4.114

I\region, 50mV/div. Bottom trace: correct phase nulling, 5OmV/div.Resistive load, timebase 0.5ms full scale.Fig.6. above. Same as in Fig. 5, except bottom trace recorded withcapacitive load. showing increased phase error.

_#

50 mV--

20mV

4

0-6.11ms

Fig.8. Class B output transistor currents (recorded as voltagesacross the emitter resistors) with zero current level shown forcomparison. Vertical sensitivity 50mV/div., R(e) = 0.4ohm. R(L)4.Oohm. 1(q) = 100mA. Bottom trace shows the error signal at2OmV/div. Time base: 2ms full scale.


-2v

4

oimv

4

Inv

4

-0. If I

Fig.9. Class NSB operation with 100mA quiescent current shows notrace of phase error and no crossover spikes. Top trace: 2V/div.,middle trace: 0.1mV/div., resistive load, bottom trace: 1.OmV/div.,capacitive load, timebase: 0.5ms full scale.

1-

Fig.10. Same as Fig.9 except bottom trace 0.1mVicliv. recordedwith capacitive load: timebase 5ms full scale.

CONCLUSIONS

Although further investigation is neededseveral conclusions can be readily drawnfrom the data presented:

Class B amplifier generates crossoverdistortion until the output signal currentfalls below the level determinated by theratio of load impedance to emitterdegeneration resistances and quiescentcurrent setting.

When crossover spikes are present aphase error is also generated'.

Phase error is inversely proportional tothe open -loop bandwidth of the voltagegain stage.

Phase error is also dependent on the ratioof the amplifier output impedance to theload impedance.

The envelope of the phase error signalstays in fixed proportion to the outputsignal envelope until a threshold isreached and it suddenly disappears(switching phase modulation).

In complex signals the individualcomponents are differently affected: thehigher the frequency, the greater thephase error. This, and the previous pointmean that phase coherence is lost duringthat part of a musical signal which bearsdominant localization and 'definition'information.

A cost and bias level compromisecombined with thermal stabilityrequirement has forced many designersof commercially equipment to underbiasthe output stage (for comparison, see ref.8).

As a consequence, comparing amplifiers ofdifferent design shows differences thatdepend on open -loop bandwidth and gain aswell as on output impedance and quiescentcurrent setting. Also, using the same loud-speaker load doesn't guarantee freedomfrom load -induced differences.

Regarding audibility of the describedperformance bear in mind that manysubjective evaluation sessions have reportedobjections which could be attributed to lost

phase coherence. Unfortunately, I have nomeans of performing a well -controlledlistening session; someone with moreexperience in this field is invited to contri-bute. Of course, when listening tosome digitally recorded piano I coulddefinitely express my preference for classes Aand NSB performance, even though notbelonging to the "golden eared" category,but the opinion of a single person land astrongly biased one who also knows what tolisten for) can hardly have statisticalmeaning.

In fact, the phase errors recorded are ofthe order of 0.05 degrees at middlefrequencies increasing up to several degreesat the top of the audio range, measured witha resistive load. Reactive loads and/orreduced open -loop bandwidth produces evengreater phase error but to standardizemeasurement a reference reactive load andbandwidth are required to be defined.

But equally important, a statisticallymeaningful definition of the audibilitythreshold to switching phase modulationwould be welcome. Only in regard to thisthreshold can the data presented hereundergo relevant evaluation.

Finally, it has been demonstrated thatboth class A and class NSB are free from theeffect described, thus highlighting theinherent quality of the NSB principle as asolution for crossover distortion.

References1. E. Margan. Add-on current dumping,

Electronics & Wireless World. 1985, October,p.40.

2. G. Nalty. Feedback letter. Electronics &Wireless World. 1986. February. p.42.

3. M. Clogolja, "Biasing circuit for the outputstage of a power amplifier - the Vh.multiplier". RCA application note AN 6297.

4. S. P. Lipshitz and J. Vanderkooy, "The greatdebate: subjective evaluation", Journal of theAudio Engineering Society. 1981, July -August, p.482.

5. P. Blomley, New approach to class B amplifierdesign, Wireless World. 1971, February, p.57,March. p.127.G. C. Haas. Design factors and considerationsin full complementary symmetry audio power

amplifiers, Journal of the Audio EngineeringSociety, 1968, July, p.321.N. S. Pass, Active bias circuit for operatingpush-pull amplifiers in class A mode. USPatent 3 995 228.1976, November 30.

6. P. J. Baxandall, Audible amplifier distortion isnot a mystery, Wireless World. 1977.November, p.63.

7. M. Otala, Nonlinear distortion in audioamplifiers, Wireless World. 1977. January,p.41.

8. J. Lohstroh & M. Otala, An audio poweramplifier for ultimate quality requirements.

acoustics, 1973, December, vol. AU -21. no. 6.p.545.

9. E. M. Cherry, Nested differentiating feedbackloops in simple audio power amplifiers.Journal of the Audio Engineering Society.1982. May, p.295.

10. M. J. Hawksford. Distortion correction inaudio power amplifiers, Journal of the AudioEngineering Society. 1981. January -February, p.27.

11. M. J. Hawksford. Distortion correctioncircuits for audio amplifiers, Journal of theAudio Engineering Society. 1981, July -August, p.503.M. J. Hawksford, Optimisation of theamplified -diode bias circuit for audioamplifiers, Journal of the Audio EngineeringSociety. 1984, January -February. p.31.

12. S. Tanaka, New biasing circuit for class Boperation, Journal of the Audio EngineeringSociety, 1981. March, p.148.

13. E. M. Cherry, a new distortion mechanism inclass B amplifier, Journal of the AudioEngineering Society. 1981. May. p.327.

Appendix 1 - Phase error calculationThe error signal undergoes phase modulationduring the first rising edge of the output signal.Fig 5. whereupon a fixed phase relationship isestablished. If we neglect the exponential ampli-tude decay term as it is present in both the inputand output signal as well as in the error signal, andlabel the input signal as sine, then the error signalis clearly a cosine. Looking at the amplitudenulling network under the correct nulling condi-tion:

reference signaloutput signalerror signal

turn to page 709

x=Asinwt= B sin bot+e)

z = C cos wt


NEW PRODUCTSSynthesizedfunction generatorA fully programmable 2MHzsynthesizer/function generator withhigh 30V peak -to -peak output andeight -digit resolution has beenintroduced by Philips Test &Measurement.

High output accuracy andrepeatability is guaranteed in thePM5191 by direct synthesis of anoutput signal from a crystaloscillator reference, ensuring thatthe stability is as good as that of thecrystal. Phase noise is less than80dBc/Hz.

Sinewaves, triangular signals,pulse trains and positive and negativeramps are the five outputs provided,with amplitude modulation beingpossible both internally andexternally. The high output voltagecan be set in r.m.s, peak -to -peak ordBm. a.c. and d.c. settings arecompletely independent within the± 15V window.

Manual operation is designed to hesimple, with logical grouping of frontpanel controls and clear led readoutof waveform, frequency and outputsetting. Frequency -related settingscan be made precisely with numerickeys while preset frequency and levelsteps can be accessed by up/downbuttons. The instrument can beoperated remotely through a GPIBan incorporated into an automatictest system. Pye Unicam Ltd. YorkStreet. Cambridge, CBI 2PX. Tel:0223 358866.

Spectrum and logicanalysers for hireInstrument Rental now have two ofthe newest offerings from Tektronix.The 2710 is a low cost highperformance spectrum analysercovering the range 10101z to1.8GHz. Due to the user-friendlydisplay and no less than five separateparameter menus, the instrument'soperation and set-up procedure isboth quick and easy. Featuresinclude a marker mode to give directreadout of frequency and amplitude,automatic signal centering, userdefinable key steps, and waveformstorage of up to three separate traces.

The Tektronix 1225 is a new logicanalyser. It consists of 48 channelsrunning at speeds of up to 100MHz inasynchronous mode. Like the 2710,the 1225 is extensively menu drivenwith the bArt. Illitlir111111 vr«,ntrnl,

for data entry and function selection.Features include glitch capture.multiple time bases, 2K of memoryper channel, built in battery backed,real-time clock and non-volatilestorage for eight front -panel set ups.Instrument Rentals (UK) Ltd,Dorcan House, Meadfield Road,Langley. Berks. SL3 8AL. Tel: 075344878.

Static testerreaches 25kVSchaffner EMC's latest electrostaticdischarge tester, the NSG 432, willgive test voltages of up to ±25kV.Part of the expanded NSG 430 seriesof test equipment, the new tester hasa multi -turn potentiometer to enablesetting the voltage with betterresolution, from a minimum value of2k1': hot rther than rely (.n the

potentiometer's linearity, thedesigners of the 432 haveincorporated a digital voltmeter. Allmajor test standards are catered forby the increased output available.

The instrument is supplied with ahuman -body model simulation toIEC801-2 (150 ohms, 150pF), butother models can be simulated onrequest. The purchaser may specifypositive or negative polarity (positiveis standard), an E -field adaptor or anH -field generator which produces anassociated burst of electromagneticradiation. For semi -automatictesting. there is an optional counterwhich produces a preset number ofdischarges in succession. The NSG432 has been designed so that futurechanges in standards can be met bysimple modifications. SchaffnerEMC Ltd. Headley Park Area 10,I leadley Road East, Woodley,Reading. RG5 45W. Tel: 0734697179.

NEXT MONTHOptical fibres. Short -haul optical-tihi edata communication is an essential partof modern communications systems.This feature presents an overview of thetechniques employed and the hardwareavailable.

Pioneers. Next in this gallery of thefounding fathers of electricalcommunication is Oliver Heaviside, theirascible genius whose insight into thephysics of cables made long-distancetelephone calls a practical possibility.

Tone generation system. Amicrocomputer scans two electronicorgan keyboards and a pedal board,controlling up to 15 generators, whichcontain eproms holding the waveformscorresponding to 16 different stops.Attack and decay times are appropriatefor each frequency and tone colour.

Q and stability. A further look at Q, withreference to the stability of oscillatorsused in timekeeping.

ELECTROINICS& WIRELESS VVORLD

AUGUSTIIIP KI

Short -hauloptical fibres

Heaviside -champion ofinductance

Curls, divs,vectors andscalars

Clearer.simplerflowcharts

Variable -speed, C -format v.t.rs

Satellitebroadcasting

(Allis and divs. Having mentionedMaxwell recently, /W finds himselftaken to task for not explaining vectorfields. It turns out to be not too difficultand certainly not stodgy.

A new look at gain/bandwidth product.The received wisdom is that the gain/b.w. product of a feedback amplifier is aconstant, with reduced bandwidth athigh gains. Is this true, or is it simply amatter of circuit design?

Variable -speed video. In the three yearssince our original series of articles onthis subject appeared, the technique ofreplaying C -format professional v.t.rs atvariable speed has advanced. JohnWatkinson deals with the newdevelopments.

Image localization. Using the wavefrontreconstruction approach to predictimage position in stereophonic soundsystems with interchannel phasedifference.


PRODU[NE BRITISH ELECTRONICS WEEK

Credit card memoryThe Aston Card has been given manyadditional applications. This credit-card sized memory plugs intoequipment designed to use it or intoa special adaptor to provide additionram. rom or eprom to a computer orother digital device. An adaptor andplug-in p.c.b. has made it suitable forthe IBM PC in addition to theadaptors already available for anumber of other computersincluding the BBC, Commodore andAmstrad micros. Originally foundedaround eproms. the range has nowbeen extended to include lithium -hacked static ram (up to 1Mbyte) andeproms. either of which can be usedas a removable. solid-state, disc -likestorage medium. Software providedwith the system allows the cards to beformatted and the computer willtreat them as if they were discs.Masked roms for specific applicationscan he produced.

A 4-4, too

Some applications are securityaccess, remote data capture andevent recording, font and characterchanging in printers, software forprogrammable machines and so on.Further details from Cumana Ltd.The Pines Trading Estate. BroadStreet. Guildford. Surrey CU3 3B11.Tel: 0483 503121.

1Mbit dynamic ramsHigh speed and low power are thelatest developments in Toshiba ramswith packaging in standard dual -in -line. plastic SOJ and ZIP formats forapplications flexibility.

The new TC5110110P/185 featuresan access time of 85ns and a page -mode cycle time down to 50ns. Thedevice is suitable for high-speedmicroprocessors operating at up to16MHz.

The TC514256PL has an operatingpower figure of 358mW reducing to5.5mW on standby. Access time is10Ons. As the standby current is lessthan 11)(11.1.A this device can replacec.mos rams in large battery -hackedmemory arrays. Toshiba (UK)Limited. Semiconductor Division.Frimley Road, Frimley. Camberley,Surrey. (a116 511. Tel: 0276 62222.

Spectrum analyser fromRohde & SchwartzThe FSA (Frequency SpectrumAnalyser) from Rohde & Schwartzoffers a dynamic range of 150dBm ina 611z resolution bandwidth.Covering a frequency range 100Hz to1.8 or 2GHz, the FSA meets mostrequirements for the measurementof spectral distribution of signals.The quasi -continuous i.f. resolutionand synthesiser tuning render theinstrument suitable for both sweptand fixed frequency analysis. Allfunctions can be remotely controlledvia the GPIB bus: thus ensuringsimple integration into larger testsystems.

The FSA facilitates the highestavailable frequency accuracy by theuse of synthesisers throughout theinstrument. With bands above5M11z; synchronized start and stoptechniques are employed - smallerbands use phase synchronizedfrequency steps. The FSA offers anintermodulation-free range of>100dB together with low s.s.b.phase noise of < -114dBc at 1KHzfrom the carrier. The resolutionbandwidths: typically 611z to 3M11z;the frequency span 1001Iz to 2GHz

and the level display range of 175dB( -145 to 30dBm) make the FSA idealfor all applications of selective levelmeasurement.

The FSA offers high operatingconvenience with parametervariation via step keys, direct entry.spinwheel or menu -dependentsoftkey operation. Automatic testroutines include correction routinesfor level, frequency and bandwidth,internal self -test, adjustableautomatic coupling for resolutionbandwidth, video bandwidth andsweep time, help functions,autozoom and autoranging. The FSAincorporates a 9in (228mm) colourmonitor with free choice of coloursfor traces; graticule; softkey labellingand background. Further features ofthe FSA are a.c./d.c. coupling;integrated a.m./f.m. demodulatorand loudspeaker; Centronicsinterface and user port. Alsoconnectors for external monitor;headphones and keyboard. Rohde &Schwarz UK Ltd. Roebuck Road,Chessington. Surrey KT9 1LP. Tel:01 397 8771.

Tailor-made connectionsFlexicon have set up a full-timespecial -projects team for bespokeconnectors. Among their recentproducts is a low -profile chip -carriersocket which uses elastomericinterconnections to provide up to224 ways. The socket projects only2mm above the surface of the p.c.b.and can be surface mounted. Holesare needed for the fixing andorientation of the socket. Mountingthe chip exerts a minimum of stressand distortion to the p.c.b. Thedesign ensures correct polarity andorientation during assembly.

Other specialist connectors havebeen a zero -insertion -forceinterconnection system for flat -screen display panels and a high -density low -profile connector for theexpansion modules of the CambridgeComputer's (Sir Clive Sinclair's) Z88computer.

The company believes that there isan increasing market for bespokeconnectors which are designed into asystem rather than being added as anafterthought. Flexicon Systems Ltd.Hitchin Street, Biggleswade, BedsSG18 8BH. Tel: 0767 312086.

GTO snubbercapacitorsSnubber capacitors are designed tocarty the full load during the turn-offperiod in gate -turn-off thyristors.The capacitors produced by LCRComponents have a peak currentrating of 2000A. The very short turn-off phase of some applicationsrequires the capacitors to have a lowinductance of about 30nH, highr.m.s. current carrying capacity of75A and a high dv/dt pulse rating of2000V/p.s. The capacitors areavailable in the range 1.5 to 4mFwith tolerances of ±5 and ± 10%.LCR claims to produce the largestrange of capacitors in the UK. LCRComponents. Woodfield Works.Tredegar, Gwent NP2 4BH.Tel: 049525 3131.

Surface -mountedresitors andinductorsBICC Citec have produced a numberof surface -mounted resistive andinductive components.

The 3204 is a fully sealed chippotentiometer, suitable for dip orwave soldering. Range available isfrom 5000 to 1MO. with a powerrating of 0.1W at an operatingvoltage of 20V.

Resistance in the 3305 trimmerpotentiometer ranges from 10 to2M0. It is believed to be the first fully0 -ring sealed chip trimmer. It has apower rating of 0.25W at 70°C withan input voltage of 20V. Temperaturestability is within 100p.p.m.

Also available on 12mm-tape reelsis the 3600 range of chip inductors.with a range from 0.22p. to 220mH.with an operating temperature from-25 to +85°C. A tolerance of 10% isoffered on values above 3.3mH.

Citec has also produced chipresistors and resistor networks forsurface mounting. BICC-Citec Ltd.Westmead, Swindon. Wilts. SN57YT. Tel: 0793 478301.


MicroProcessor Engineering Ltd133 HILL STREETSHIRLEYSOUTHAMPTON SO1 5AF

FORTHSFor IBM PC and CompatiblesModular Forth - award winning Forth 83 £475.00very fast, multitasking, GEM, modules, 8087 fpWorkFORTH

Viewtrace DebuggerSoftware Floating Point80 x 87 Floating PointWindows & GraphicsDocumentation Tool Kit

WorkFORTH Development Kitincludes ViewTrace, SoftFP, Doc Tools

For 680 0 SystemsMPE-Forth/68K 0S9/68K - fastMPE-Forth/68K CPM/68K - fastGEM-Forth/ST Atari ST - GEM i/f, fastMVP - Forth AmigaMM MasterForth MacintoshOthersUniForth for RT11, RSX11, VMS

(inc micro)

righV

£45£45£45£45£45

£145

£375£375

£65£150£125

£175-£675

0

aTel: 0703 631441

Software & Tools for EngineersCROSS -COMPILERSFor PCDOS, MSDOS, 0S9/68K, CPM/68KCPM80. OS9/6809, FLEXfor generating new Forth applications, includingROM based turnkey systems fast, interactive,debuggable code, high or low level interrupts,technical support, source code, debug &download tools, cross assembler included.Practical solutions to real problems.Cross Compiler core £250

Targets include source, RAM and ROM versionsForth -83 targets £225

Z80, 80 x 86/8, 680 x 0Fig -Forth targets £175

6502/110, 8080/5, Z80/64180, 80 x 86/8,1802, Z8, 6800/6303, 6809, 680 x 0, 99xxx

Forth -79 targets £350Bryte Forth 8031/44/51

HARDWARE for PCsEPROM Programmer 2716-27512 £145PAL Programmer MMI, NS, TI 20/24 pin £325GALJEPLD Programmer Lattice/Altera

20/24 pin £350NOVIX 5Mips co -processor - ready for

NC5000MVP Microcoded - includes microcode tools £1225

£852

ENT12.1t 51 ON It F.I'LY CAM)

'Ac sell all types of test equipment fromthe simplest to the most sophisticated andspecial ised.

All of the high quality second userequipment we supply is fully calibratedand meets the manufacturers originalspecification. All equipment is fullyguaranteed.

We also buy good quality under utilisedequipment.

CARSTONELECTRONICS

Used Test Iguipmern

Mock lionAutumn 19114

01-4) lonry

ENTER 57 ON RE1'1.1( CARD

HIGH QUALITY - LOW PRICES

4-11GHz SATELLITE TV RECEIVING EQUIPMENTRECEIVERS, LNB's, LNC's, FEED HORNS,

ANTENNAS, ANTENNA POSITIONERS,POLOROTORS, LINE AMPLIFIERS, ETC.

For further details contact

HARRISON ELECTRONICSCentury Way March Cambs PE 15 80W Tel 10354151289

IC OMCommunications

ICOM introduces the II' F. )oc advanced technology cciitiiiiiocscommunications recer:--! With 99 programmable memories he IC-P7C,Ycovers aircraft marine FM nroadcast Amateur radio television and weathersatellite bands For simplified operation and quick tuning the 1C -R7000 featuresdirect keyboard entry Precise frequencies can be selected by pushing thedigit keys in sequerce of the frequency or by turning the main tuning knobFM Nide FM narrow AM upper and lower SSB modes with 6 tuning speeds

I 0 5 10 12 5 and 25kHz A sophisticated scanning system provides instantaccess to the most used frquencies By depressing the Auto -M switch theIC -F7000 automatically mertorises frequencies that are in use whilst it is in thescan mode this allows you /o recall frequencies that were in use Readout isclearly shown on a dual-col bur fluorescent display 0p' -7., PC -12infra -red remote controller voice synthesizer and HP -

release rush me details of the IC -R7000 and my nearest ICOM dealerName

Address

TelPost to: ICOM (UK) LIMITED , Dept WW, FREEPOST,

LHerne Bay, Kent CT6 8BR. (no stamp) Tel 0227363859. -F:NTrAt 29 ON IO:PLY ('.\ Itl)


LANGREX SUPPLIES LTDClimax House, Fallsbrook Rd., Streatham, London SW16 6ED

RST Tel : 01-677 2424 Telex :946708 RSTSEMICONDUCTORS IP// 11

1

\44/ I II I 1

II I I

144/1 1 II 1 1

\I 110 01P/\ 1 12

I \ 1 I, 1

1,1 11 11,

1 41',i 41,1:1:\\\112 1111,

\\11 110`\ 414 1111.

1( 10- 1( 1114 0 111( 10. II 14I( III 11121( 114 0 12tt II, iit( 110 II II)14 117 II 2444 I Is II 111 11 17

tt 12, 0 1,II 120 0 2.it I1, 21

It I 1, o 2141117 11 21

I( 147 ,11

1( 144 II1( 14)14 1,71( I,S 11 11

1( 1.41 II 121( 107 II III1( 1-11

I( 1.'11( 1724 I

ItIIIIIIIt11

11

IIII

I4

itIIIIII

11

1 11 211

:4, II 1-1

11/

II 4,II illII 111

II 111

\II II 111

0,1 11

1,2 10

Is: II 41

Isl 10

Is, 11 III104 11 I:P4, 0 I,1.0107 11 l'1111 01 1

'24 11 17

'11 12

'14 II 13

10

11 10

II 111

14, II 3111.17

114 11mi121 4 0042S 31/

VALVES11

\111

.11111

BASES

III''4"'1 I 1 1 40

s io1

I

11

1'I Ill

1 1111

CRTs

141

441'1' -1"411'I III

I412 ,114 1 111Aril 1 00

IA

I4:

20 011NM

's1 I I,2 111111

2' 411\1 4 4444\1 41 211 111

.111 1.4414'

11 4 004'%11,1 IN/

1/14 IS IN IK177 lold

1 loll 171111K S.S1.,,1,1

1 11111 211.1\1\1111 2311

\%,,2 24111 241

12 14,241 S 2,

i 017`.2 Iv.

22 1 111 2,111.11

"10 1, SOS 111

I,11111

011 III 111

II 7,:7 12 2,

411 0 1111

,1112

14 7:0

.14

1i

It 1

1' 1111

4 1,

1.11111C

pw 1111,

1,111 114b

1,111 01.

SIIN 0 11

\ 10 1 111

1 4411 I IIISs1 11_\As, II 24

4ss.1 II 2s

1,1 II 2s4 I ' 11 2,

11,1 II 110

1'111 IIissj.. II 72

\ 2.. II 271S421 112711114, 10'117. 411111 1 1111

III: I211

tl 714' 1 '1,I 4.w,I )1111

I 21.

1271/4401

Scot,

/I ul

II/ I 111141145

14/1 '1:'.1145

111.14%1 111 .

11411( 141 1111

11 \III \ 11

/1"1

101( 4/ 41'( :111

14 117 I

14 1111 I

( 44 I

( 4,1'((11

1.

Pt l Is./I'l'l sir, 1

Pt (:11M.11 s2Pt I toPt 1 s2Pt I SI.('(1 47P1.1 2111Pt 1 21111.1 I S111

I.( Isle1'1 I so, 1

70

11'14"' 1 711

11 14w 1 711

1.1417" IMFPl I SiP( 1 s1

s,Pt I

Pt( ,44146:1.1),1111('I 14,411% I 001.1 1 21141 4411

1'11PI NIPI A 111

PI 42 ,11

I'l 4.1 411'1 4 III

:111.1w :021.VII

1

) 13'111 (41

s' I ,11

MS -1 I 2,P11' 21111

P44/41111 141P1411 141()1 4.1 I 41 .111

()1)\'11-2.1. 14 11100A111.111 21, 24

Is IsI)1)\41,.111,\

14,111(X)A117.i0

71. 1,1

1)1)/11.4 111A1'7711

1)1 17 12

1.1\ 01 12 1.

2100211.1'1.11

-0.1

-111,1

-1111

III 1041111\ III

`'II1.11.211111 2'0-1011 111-KIP1 101

(114

441P1 1111

NIP4A111.

K IPM Ill%IPS( oriKIPS1

[SKI 4111NI.: 11111%Is 1 4114

444770

'\7"

.y/i

142.1,42112

I.V2H/A/2111\/201

I \/1 \ /211-I( II.II 211

1 X 141 di I Ill /144,11 11 1411( 24 41 21 /1444414 11711

IN 2./ 4414 1114 / II 70IX 1 1111 41 II Y. /I \ 4,11 II 2,IX 10 4 110 I II 2, %III 4 001

X 11 I 211 11 2, 14,11, 11 111

1( J7 1 .41 11 41 4.41111 01I 1 II 141 . I \ 11 011 0114

41 I 11 14. 4.40111 114

II 47 4.41114 11114

111 11 In 4.41111, 111417 4, %Mini. 1114

%411117 III'''4 4, 4.411110 1111',

1 10 11 II 4, 4/4145 110,IN 71.

1 ' 17 114\ 4.,41111 4

11(1' 11 4, 4.S4111 III1X.4411115 4444

I I( sI/ III 11 5, 44290 11 3

4.7 111, 44,171 II 1

IN 51 2 11X, NOM o11(14 110 0.11 7(1417 1 ,14 122 511

0(421 1,311 ' \ 4144 I

111 11,1 12110 ' \ ON, II 1,

I I( 411 Is 11.1

II 141 Is 111 /171 '\4'w ',.II( 1711 4 41/

I( 171 4411I II 7111 1110

)1 2111 , \ 1117111 2112 \ 110,11 1III 411 \ 1/1 11

1 :III 704 II 411 I.

1 It 70, (1111 101 III(4 211/, ,4 \ :112 411III 741' 101 II I 1

IN 1'7I 7 ,1. I \ 104 111111121.12 741' /14111 1111N2114,1) 1 / 144 114 142,1421111,1 4,111 11 1 1

1221111111 P. .11 1111III II

2N21 1 .1111

214. 2145

74.22Is 41 .12

24.2219 0 124.2221 11 22

N222111 224.2222 11141N2223 7

4.21,11 11 2;%nig 11 2;4.' 114\ 117:

11 111

III1141

\"1117111;2.

\p124 1117s.2,125 11 22

11 12'.1111.1 11.41

N.11134 11 171

s k155 ii 711'\14411 11111

\1441 II 7:1142 11111,14 I41

'\1707 II II'\1711 1111

1704 11 I I

'\1711, II 1 I

1711, II II'\1717 11 11

1710, 11 I I

1700 1111 1710 II II\ 1711 III'4 1771 1

1772.0771 1.114 1570

'\1.v`4.111142441,4I:21%1411,

74.411,\2%411,11

21441102h4oid2h414,221412.12%412,2N4241,21,12ss21s42sii

21,4411121%44.221%51,72N,4,s2N,Poi

2,011.42'41121

2%112'

2!012,.4111121111'

274-%2s74,,,

INTEL

11101,441 \7',414111411

\ -2,11 sl I '

44'11SI 1'

IN, \I.

/111Is 70III I

17

'AIR so,41 47

I1(41so

'('( 54'(.44.44

( 11421 Isl

1 1 s21.441

RATED CIRC

\

UITS

In!

-( 4

I

11.. ,41

1111

(.7 7',IIh( IllI I 1 1111

lb 1.4 7.\14 111

11,1,

'1)1,I1\

114

I'

11711

17,41'7.\ 1

1'111 \4422

\\ 2

44444 I

(4 13''(44

' \1,\V41

011211111

II( 1

I

1

I

07,

".4'

l'l

+111,..,1.11,1 1,

'007u741811.41.17A..00711 IN,

r.141.A.04141..1i1/11 I

.1101

..2111

.44421.

'4171-02s'1127.

"47'141144

.044,I 41'1171'4412 I

1,1444

I cslvtlI \ I11 \ 21114 511

\ II, I..,

I. tins ..1 ('1('Uand pack1142 .1,,...1141,...M,ConduCtors I. 1 IMI , 11< I' 41:11 1:\1 ,,,1,1

('rice ruling al time of despatch.In sonic cases prices of Mullard and l'SA salves will he higher than those ads ertised Prices correct u hen going to press.Account facilities aallable to approsed companies with minimum order charge 1111 Carnage and packing 11 .non credit orders(her 111111101)pes of s als es. tuhes and semiconductors in stock Quotations for any Is pes mil listed. S A E.

Telephone 01-677 2424 7Telex: 946708E. & 0.E.Open to callers Monday -Friday 9 a.m. - 5 p.m. WW



STEW PRODUCTSPiezoelectric filmPolyvinylidene fluoride Ipvd0 in apolarized form, with metallicconductive surfaces applied, offersremarkable piezoelectric propertiesand may be used for a seeminglyunlimited number of applications intransducers. It acts as a self -chargingcapacitor with the signal taken fromthe metal electrodes. Like piezo-ceramic material, it produces anoutput voltage when stressed andwill change its physical dimensionswhen a voltage is applied across it: soit can he used both for microphonesand loudspeakers. As a load cell it canhe used in pressure. strain, vibrationand impact measurement. and inaccelerometers. It has been used toprovide touch sensors forexperimental robots. and respirationand heartbeat sensors for babies. Thesimplest example is its use as a switchand with 20 times the output of aceramic transducer, proportional tothe applied stress, it can drive aliquid -crystal display directly. Thefilm can be incorporated intokeyboards where the switches havethe advantage of dirt and moistureresistance, bipolar output and theability to be used in battery -poweredequipment. One specific successfulapplication has been in itsincorporation into a pressure -sensitive graphics input tablet withan x -y accuracy of 0.1mm.

1 he film also responds to infra -redradiation and can be used fortemperature measurement. It issensitive enough to detect a humanbody at 16 metres and beincorporated into intruder alarms.Further details, samples.experimentation kits and the filmitself are available from the PennwaltCorporation. 74 Great King Street.Edinburgh E113 6QU. Tel: 031 5581144.

Solder reworkstationA new 11 cl ler multi -function hot gasworkstati. in is suited to rework andreflow soldering/desoldering ofmicro components. The Al 11700station features a hot -gas pencil.giving a variable rate of gas flow, thetemperature of which is adjustablebetween 10°C and i50°C. Gas flow isturned on and off by means of afootswitch. A hand-held vacuumpick-up tool, connected to the workstation. enables components to hepositioned or removed during reflowor desoldering. A temperaturecontrolled hot plate. adjustablebetween 30 and 250°C provides pre-heating for ceramic or othercomponents with poor heatconductivity. Weller equipmentcomes from Cooper Tools Ltd.Sedling Road. Wear. Washington.Tyne and Wear N38 9132. Tel: 091 416

BRITISH ELECTRONICS WEEK

Fast charging of NiCadsAfter extensive research into thebehaviour of nickel cadmiumbatteries under various pulsedcharging conditions. Rediffusionradio systems have developed aprocessor -controlled battery chargerthat is capable of sensing thecondition of the battery andrecharging it accordingly. It isintended for use with the smallerNiCd batteries commonly used inhand-held radios and other battery -operated equipment as used bypublic and emergency services.

At the heart of the BC25 charger isa patented system for recognizingthe fully charged state of a battery.Having this ability, the charger canhe used to rapidly charge each

battery safely with no risk ofovercharging. It can also he used totrickle -charge batteries only partlydischarged. A full condition charge.i.e. a controlled discharge followedby a rapid recharge. is used forbatteries that have failed or may hesuspect. I.eds are used to indicate thestatus of each battery under chargeand, in the condition mode, thecapacity of the battery as apercentage of its rated capacity. TheBC25 is fully automatic and onlyneeds the batteries to he loaded andremoved. A manual switch alternatesbetween normal or conditioncharging. Rediffusion Radio SystemsLtd. Newton Road. Crawley, WestSussex. RI110 2PY. Tel: 0293 518855.

Pulse/echo cable fault locatorThe first truly hand-held. battery -powered, pulse -echo cable faultlocator with I.c.d. read-out is claimedby Cossor. It has been designed to hecomfortable and easy to use by anyoperator. The CFI. 510 us&microprocessor technolgy and theI.c.d. is a dot matrix type with fourranges: 100m. 300m. 1000m and3000m full-scale. with 1.6%resolution and a nominal 3%

accuracy.The pulse width is selected with

each range and velocity factor set to0.67 at switch -on and is adjustablebetween 0.01 and 0.99. With a weight(4 only 1 kg. the CFL 510 is poweredby six AA cells with a battery life of upto three months normal usage.Cossor Electronics Ltd. ThePinnacles. Harlow. Essex CM I9 31313.Tel: 0279 26862.

Graphic chip setNew from Ili-Tek Electronics is theNational Semiconductor advancedgraphics chip set, a v.l.s.i. systemwhich utilizes parallel processingtechniques to enable handling of anunlimited range of colours with noreduction in performance.

The chip set comprises individualmodules which enable the user todesign a system to meet specificrequirements. Modules can heintegrated with a general-purposemicroprocessor for black and whitedisplay or used to support unlimitedcolour planes for a highperformance, high resolution colourgraphics workstation. plotter, orprinter.

Modules in the chip set include a20MHz raster graphics processortr.g.p.) which has line drawingspeeds of 10 million pixel/s in anydirection and a powerful instructionset, enabling the user to incorporateproprietary graphics algorithms intothe system: a 20MHz 'habit'processing chip which, dedicated to asingle parallel memory plane.enables additional planes of colour tohe added without degrading systemperformance: a video clock generatorwhich uses a low -frequency crystaloscillator and an on -chip digitalphase -locked loop to produce a pixelfrequency of up to 225MHz: and a225MHz video shift register whichhas a 4 -word 16 -bit fifo buffer to easetiming problems.lii-Tek Electronics.Ditton Walk. Cambridge. CB5 8QD.Tel: 0223 214722.

Low -profile toroidsTo meet a demand for compact powersupplies and audio equipment. DrakeTransformers have developed a rangeof low -profile toroidal transformers.The PWL range has about half theheight of conventional toroids withequivalent ratings hut have a greateroutside diameter. They havepolyester tape insulation and sleevedflying leads. The PWL transformersare offered in a range from 100 to800VA.

Drake is now an independentcompany. having bought itself fromits former parent. BlagdenIndustries. This has resulted inmaintaining employment for 76skilled workers. while moving to anew address near their formerfactory in Billericay. DrakeTransformers Ltd. Bruce Grove.Wickford. Essex SS11 8BT. Tel: 0268560040.


LENEW

BRITISH ELECTRONICS WEEK

High-speed 10 -bitd -to -aTwo ultra -high-speed digital -to -analogue converters have beenproduced by Datel. The ADC -510and 515 can complete a 10 -bitconversion in 425ns and 650ns.giving sampling rates of 2.35 and1.54MHz respectively.

Features include initial errorsof 3 I.s.b. maximum for offsetand 51.s.b. maximum for gainerrors, different codingselections, indication of signalsbelow and above the full-scalerange and the means to improvethroughput by putting a sample -hold hack into the sample modebefore the existing conversion isfinished. There is a facility toprogramme the input voltagerange. Other specificationsinclude a maximum nonlinearityof ± 0.5 I.s.h, a minimumharmonic distortion below fullscale of 60dB, and hightemperature stability. Moreinformation from: Datel UK,Intec 2 Business Park, WadeRoad, Basingstoke. Hants.RG24 ONE. Tel: 0256 469085.

Eraseableprogrammablelogic arrayAn eeprom-based programmablelogic device from Exar is claimed tohave logic capabilities comparablewith gate arrays and allows the use ofmulti -layer logic. The XR-78C800contains the equivalent of 600 to 800gates. Advanced logic architecturepermits umlimited Boolean levelswith up to ten flip-flops at any levelwithout using i/o pins. Term sharingat any level and logic -controlledinput latching are other features.The devices are designed to integratea wide variety of user -defined logicfunctions onto a single package andoffer a fast turnaround to save timeand hoard space. The device is addedto a wide range of electricallyeraseable proms including two high-speed c.mos eeproms. ExarCorporation. 43 Moorhridge Road.Maidenhead. Berks. SL6 8PL. Tel:0628 783066.

Multi -purpose logic analyserThe Gould K50 can he configuredfrom the front -panel keyboard from32 channels at 25MIlz (1k samplesper channel) to eight channels at100MIlz (4k samples per channel). Itcan capture complex timing. stateand microprocessor- orientedsoftware events. including glitchesdown to 5ns. which are stored in aseperate memory and can heunambiguously displayed alongsidetiming data.

Three external clock inputs withqualifiers are provided to allow thedemultiplexing of complex events.while Gould's 'Trace Control' featureoffers four levels of complex -eventdefinition with four trigger wordsplus one glitch word.

The K50 features a high -resolution, non -glare 7 -inch(178mm) c.r.t. which can show up to17 channels across the completememory or he expanded for detailedviewing.

Channels or channel groups canbe labelled. and two independenton -screen cursors and a triggermarker are used to indicate absoluteand relative data position and value.The major instrument functions are

controlled by dedicated front -panelkeys, while soft keys guide the set-upof individual parameters. The'search' and 'compare' functionsdisplay their results as highlightedevents.

The K50 is supplied with eight -channel, high -impedance probe pods11 megohm, 5pF I. which eachprovide a t.t.l. or ±9V variable -threshold range and are protected to+50V.

The analyser is supplied completewith IEEE -488. RS -232 andCentronics ports, plus trigger, re-start and video oulputs. Alsoincluded is a battery -hacked non-volatile memory which saves thecurrent stored data. three referencedata sets and 16 set-upconfigurations.

A range of microprocessor analysispackages is available, includingdisassembler software and interfaceadaptors for the Z80. 8085, 6502,6809, 8086/8 and 680(K) processors.Price of the K50 is 12950 (plus tax).Gould Electronics Ltd.. InstrumentSystems. Roebuck Road. I lainault.Ilford. Essex. IG6Tel: 01-500 1000.

Image processing on a PCA I \vo hoard plug-in for the 1101 l'CIA RT) can create an imageprocessing workstation ideal forapplications such as machine vision,image enhancement, scientific,medical, sonar and geophysicalimage analysis, high -end graphicsarts systems and simulation/trainingsystems. Design innovationsincorporated into the MVP -ATinclude 'area -of -interest' processing.real-time image operations. non -interlaced output and a 32 -hit planeimage buffer comprising four flexible512 by 512 by 8 image buffers whichcan he used in all possiblecombinations. When combined withthe capacity to performconvolutions, averaging andsubtraction, pattern matching andmorphological transforms, this will

give the user performance previouslyavailable only at a much higher price.Other functions offered by the hoardare pan, scroll and zoom, real-timecolour frame grab from a variety ofinput sources such as RGB or NTSCColour. RS 170 monochrome. andmultiple input and output look uptables.

The optional Matrox Imager -ATpackage is specifically designed tocomplement the MVP -AT andprovides a cost-effective solution for0.e.m's planning to develop theirown software. This package containsover 150 library routines and iscallable from 'C. Fortran and PascalMicrosoft compilers. DensitronComputers I.td, Unit 4. AirportTrading Estate. Biggin I till, KentTN16 311W. Tel: 0959 76331.

Maths on a personalcomputerA new software package (MathCAD)allows the entering and solution ofmathematical equations exactly asthey would he written or printed in amaths text. In addition it can he usedlike a programming language tocompute with variables. and toproduce graphs and tables and addtext. Greek characters can be used aswell as all mathematical symbols.The software handles real andcomplex numbers and computes unitconversions and dimensionalanalysis. Functions not provided canhe defined by the user, althoughsome advanced functions such asintegration, differentiation. FastFourier transforms, cubic splineinterpretation and statistical analysisare already included. MathCADchecks for errors before it processesthe equations, looking for undefinedvariables. mismatched units.missing parentheses and the like.

MathCAD runs under MS -1)0S 2.0or higher and is therefore suitable forIBM PC (XT orAT) and compatibles.It requires 512K of ram and IBMcolour or enhanced graphics or aI lercules monochrome card. Outputis to a dot-matrix or laser printer.MathSoft International 1.td.Tamworth. Staffs, B79 713R.Tel: 082786 239.

Contact cleanersUsed to clean, lubricate and protectcontacts and edge connectors platedwith precious metals (gold, silver.palladium etc) gold Electrowipes arelint -free pads impregnated with ablend of contact -cleaner fluid andsafety solvent. Packed in sachets. thedisposable pads use a non-flammablesolvent which is claimed to he safe ondelicate components and 'sensitive'plastics. As well as removingcontamination from contactsurfaces, the pads leave a residualtrace of lubricant which increasescontact area and reduces contactresistance to a low and stable level.Another advantage is that with thelubricating properties of the wipes. itis possible to reduce the thickness ofthe precious metal plating.Electroluhe Ltd. !flakes Road.Wargrave, Berks. (;10 8AW. Tel: 073522 3014.


CIRCUITSIMULATION

SOFTWAREFOR

AC OR DC NETWORKSACTIVE FILTER DESIGNS

COMMUNICATION DESIGNSSIGNAL PROCESSING

TRANSFER FUNCTION ANALYSISROOT LOCUS PROGRAM

STATIC THERMAL ANALYSISPRINTER & PLOTTER PROGRAMS

PRICES RANGE FROM £79.95 to £125Call now for more information

BRIGDEN TECHNOLOGYTEL: 0322 331984

WRITE .11):UNIT 24, ERITH BUSINESS CENTRE. ERI'I'll HIGH STREET,

FRITH. KENT DAB I QYENTER 27 ON REPLY CARD

HART - The Firm for QUALITYLINSLEY-HOOD 300 SERIES AMPLIFIER KITS

Superb integrated Mosf et aniplitier kits with an unbeatable pedigreecircuit design by Join Linsley -Hood and engineering by HARTUltra easy assemb:y and set-up with sound quality to please the mostdiscerning listener Ideal basis for any domestic sound systems if

quality matters to jou Buy the complete kit and save pounds off theindividual component priceK300-35. 35 Watt Discount price for Complete Kit £98.79K300-45 45 Watt Discount price for Complete Kit £102.36RLH485 Reprints of Original Articles from HIFI News £1.05 no VAT

LINSLEY-HOOD SYNCHRODYNE AM RECEIVERVery high quality kit for this recent deskgn featured in Wireless World Advanced constructionsystem approved by the Author uses 3 double sided PCBs In a stacked layout for total s:ability easeof construction and minimal wiring This module will 101M the AM section of an ultra high qualityAM,FM switched bandwidth tuner to match our 300 series amplifiers Power supply and tuning gangwill be included with the FM sectionK450 JLH Synchrodyne Kit Special Price £59.95

LINSLEY-HOOD SUPER QUALITY FM TUNERThe long awaited ultra high quality FM companion to the Synchrodyne AM receiver Novel circuitleatures ready butt pre -aligned front end phase locked loop demodulator and advanced sample andhold stereo decoder Circuits featured in Electronics Today International magazine February andMarch 1987 Complete kits for FM only Of combined with the Synchrodyne are cased to match our 300Series amplifiers Send for detailsSpecial Introductory Prices. FM only version £111 69 Version to add Synchrodyne f 18.13 Bothprices roc VAT Ai post Send for details

HIGH QUALITY REPLACEMENT CASSETTE HEADSDo your tapes lack treble. A worn head could be the problem Tapeheads are constantly improving and fitting one of our latestreplacement heads could restore performance to better than new'Standard mountings fit most decks and our TC1 Test Cassette will Citmake it easy to set the azimuth spot on As we are the actualimporters you get prone parts at lowest prices All our heads aresuitable for Dolby machinesHC20 Permalloy Stereo Head Good quality standard head fitted as original equipment on manydecks £7.66HS16 Sendust Alloy Super Head Dude simply the best Longer Ide than perma boy higher output thanferrite, fantastic frequency response. E14.86H05514. Track head for auto -reverse or quadrophonic use Full specification record and play head £14.60Special Offer Stereo Fi/ P Heads £2.494 -Track Auto -Reverse Play Head £3.50HS9510 2,4 Stereo DC Erase Head £6.70H0751 E 4'4 Erase compatible with H0551 £39.70Full data on these and other heads in our range are contained in our free list

HART TRIPLE -PURPOSE TEST CASSETTE TC1One inexpensive test cassette enables you to set up VU 1Dolbyt level head azimuth antitape speed without lest equipment Vital when fitting new heads Complete with instructions £4.66

JLH DUALITY AM RADIOSets of Parts avallaale now including Short Wave coils Full kits ready later Send for list

Send for your FREE copy of our lists with full details of our complete range of KIK CorivsinentsPCBs. Cassette Heads and Decks Overseas please send 5 IRCs for Airmail Post

add V4 T ro rn once. Piistage Oflfvders up to f 10 50p f 10 to £49 I f Over f.50 II hi

ELECTRONIC KITS LTD1, Penylan Mill, Oswestry, Shropshire SY10 9AF24 hr SALES LINE (0691)652894 Please add VAT

Fordesigntransformershalfthe improvementsanddate

Wemadeareconstanttendencyperformance,of thesewithoutrequirementsreadilyalteration

We

which

SOWTERFREQUENCY

name47 yearsmanufacture

duringWe continually

ittechniques

a veryall

types of

particularlylisted

can bequestionnaire)

price.in LOW

a few

TYPICAL

4652

AUDIO

Wehave concentrated

ofour

takeand

utilising

numberworld

Transformerstaken

size withoutPCB

cancanson

and

ANDor ex -stock.

6499

make

high gradetotal

full advantageinsulating

the

of originalbut naturally

into

mounting,be suppliedand

requestgenerally

QUICK

4079

it!on

sold exceeds

materialsmost

designs

which areaccountsacrifice

andwith

performance(utilising

without

DELIVERY

6471

theaudio

of all

up to

therein

theof

a fewor

our

*6469

it!we

which period

magnetic

largeover theSowter

These havesmall

forbelow. Theyshielding

modified

COSTdays only

PERFORMANCES

3678

TRANSFORMERSYou

the pastand

a million.

in measuringinstrumentation.

havefor clients

certaindemand.

towards

aremumetal

availablein

specialisemeans

so wter

Type No

A

3575

Descrmtior Miniature

bridging

transformer

Line output kW primary

microphone

Line output

high level low

distortion

toroidal core

Splitter

combiner

transformer

Midget mit,

transformer

for BT pnvate

systems

Very high

QUO

microphone

transformer

0 ansformer

Impedances 10C 10E

can be fed

from 50-

6000

600 or 1500

input or

outputs

Pys 60.200

cr 600(1

Sy 51(0 down

to 1k8C1

gm 6000 Balanced

Primary

Two 2000

Secondanes

Py 6000

Sy 60k0

2000 Py for

lk() loading

lElifilarl 81

step up

rpouenzy

wee

''ermrrnance

2011/20kHz 20Hz 2001z 30Hz2Okliz 2044201411 20f1:20kHz 300Hz1411z 20411.20kHz

!O le18 over

above range

:0 25dB over

above range

:0.5dB over

above range

:0.3dB

4011z-lSkHz

1.-0.5dB

2041z20kHz

10.5d8 over

above range

:0 5dB over

above range

:0 2d8 over

above range

MAIMUM

level

Maxvrfwrr

Distorbon

SIM( hog

Dimension

7.75V rms.

on secondary

1.75V r.m.s.

on 6000

en 5k11 load

148 r.m.4 al

30Hz

26dBm at

30Hz

2.31/ mi. at

30Hz

0.6Vp-p on

Primary

20VOrms on

Py at 30Hz

With 10V

r m.s at 40Hz

only 0 124

On 6000 low

source 0.1%

less than

4.1% at lkliz

0 1% al

3011z at

26dBin

negligible

0.1% at

1kHz

neeigible 0.1% at 2011z

Electrostabc

screens and

metal can

Mumetal can

if des red at

extra cost

"bimetal can Toroidal can Mumetal can

ngtd haul

bolt

PC8

mounting

*metal can

33mm dram

22mm high

36mm high

43mm

33mm

13mm diem

22mm high

50mm dram

36rnm high

33mm dram

37mm high

11 1mm high

19mm

11mm

33mm dram

22mm high

:es eat

narks

The

Phone:

1-511023

50 - 19.77

100 - 1927

(establishedBoat Yard.

0473

1-519.61

50-0889

100 /.8 69

E. A.

Cul I ingha-nIpswich

52794 &

1- 5 19.67

50-1811

100 - f.8 41

SOWTER1941) R.

Road. IpswichIP1

0473 219390

1- 5 117 12

50-115.69

100 - /1535

No. EnglandIP1

2EL. England.- Telex:

1-5114.59

50 - 113.37

100 - 11108

LTD.303990

2EG. Suffolk.

987703G

1 -5 L189

50- 13.55

WO - 1329

PO Box

SOWTER

1 - 511138

50 - 110.12

100 - 09.92

36.


ENTER 12 ON 14F:l'IN ('AN!)

749

RAEDEK ELECTRONICSSERVING THE COMMUNICATIONS AND ELECTRONICS INDUSTRIES

Tel: 021-474 6000

Telex No: 312242

MIDTLX G.

102 PRIORY ROAD, SCRIBERS LANE, HALL GREEN, BIRMINGHAM B28 OTB. ENGLAND.TRANSISTORS: VALVES:

TYPE: LIST: TYPE: LIST:E E

.'N3375 11.25 2SC1978 6.40.'N3553 1.90 2SC2053 0.802N3632 12.95 2SC2237 11.50.'N3733 12.95 2SC2287 9.60.,N3866 1 50 2SC2290 20.00.'N4416 0.75 MRF237 3.50."N4427 1.75 MRF238 11 90.'N5090 10.90 MRF240 20.70.'N5109 1.95 MRF245 33.002N5160 3.00 MRF247 33.30.'N5589 8.00 MRF433 9.00.'N5590 8.25 MRF449A 10.15.'N5591 10.00 MRF450 14.50.N5641 7 50 MRF450A 14.50.,N5642 10.20 MRF454 17.25'N5643 11 85 MRF454A 17.25

.'N5913 2.50 MRF455 16.50

.'N5944 8.20 MRF458 17.20

.'N5945 10.60 MRF475 2.30?N5946 11.50 MRF476 2.15.'N6080 7.00 MRF644 22.50.'N6081 8.75 MRF646 27.002/46082 10.90 MRF648 32.702N6083 11 95 MRF901 2.752N6084 12.50 SD1013 9.752SC1729 14.50 SD1019-STUD 23.102SC1945 3.45 SD1019-5 22.802SC1946A 16.00 SD1127 3.102SC1947 8.50 SD1134-1 2.252SC1969 1.80 SD1136 11.902SC1970 1.40 SD1143 9.402SC1971 3.50 SD1219 14.702SC1972 600 SD1272 10.95

SD1278 14.25

INDUCTION AND DIELECTRIC HEATING SPARES

INCL

CERAMIC CAPACITORSVACUUM CAPACITORSGRID LAMPS

CARBON FREE HOSE

WATER FLOW SWITCHES

,-.01 ID STATE RECTIFIERS

RECTIFIER VALVES

OSCILLATOR VALVES

COOLING FANS/FILTERSPIC PIC

TYPE: LIST:C

TYPE: LIST: TYPE LIST:C

TYPE: LIST:C

TYPE: LIST:

AH211A 13/ 50 F FYI 200 0A3 2 50 6AU5GT 3 70 813 30 00AH2511 90 00 EF95 1 60 082 2 50 6AZ8 3 80 934 18 00AH2532 31 50 EF 183 1 90 OB3 2 50 6BA6 1 70 935 41 20BTS 52 50 FF184 1 80 0C3 250 6BE6 1 95 2050 4 80BTSB 52 50 F K90 1 40 2C39A 39 90 6BH6 2 15 2050A 4 80BT 17 142 00 EL34 390 2C39WA 42 00 6BJ6 200 5544 81 00BT 17A 130 00 EL36 230 2021 290 6BK4C 450 5545 95 00BT95 125 00 EL84 300 2E26 7 50 6BN8 350 5557 24 50C3JC3JAE55LE 80CCE8OLE 88CCE 90CCE 1301EB91EBC91EBF89

30 0030 00560014 0021 003907 50

21 251 35I 101 35

ELBEEL519EL803SEL821F N32EN9IEZ80EZ81EZ90FGI 7FG105

2 107 709 95

13 7516 252001 901 501 50

24 50160 00

26253.4001E IM3-500ZEIM38283C453CX100A54.65A4.125A4-250A4-400A4.4008

114 0099 0099 0015 0024 5070 0052 5060 0076 00

110 00110 00

6BZ66C46CB6A6CJ36CW46DC66E56EA86G666HF56HS6

2 501 951 802308002 454 202.252504 253 95

5559 52 505727 2 955867A 140 005879 6 155965 2205991 32 006130 24 506146A 9506146B 9 506360A 4 956550A 79068838 8 70EC90 200 GXUI 15 00 4-400C 110 00 6JB6A 450 6973 3 95ECC32 3 25 GXU4 45 00 4832 30 50 6JE6C 6 25 7027A 650ECC81 1 90 GZ34 5 35 4C35A 135 00 6JS6C 6 65 7199 420ECC82 I 90 K T66 900 4CX250B EK7 250 7247 320ECC83 1 90 KT77 15 50 EIM AMP 55 00 6611 2 25 7262A 26 00ECC85 380 K788 24 95 4CX250B 6KD6 6 40 7360 12 20

ECC88 200 ML8536 275 00 NAT 48 00 6608 200 7586 1 1 50ECC91 200 ML 8741 265 00 4CX350A 8700 6L6GC 4 10 7587 35 00ECC189 200 NI SERIES 45150A 33 70 6106 6 25 7591A 4 65ECF80ECF86ECF801ECH81ECL82ECL86EF80EF85E F86

1 501 651 802301 901601703 00300

00V02-600V03-10OV03-120Y3-650Y3-1250'14.250RGI.240ARG4.3000XGI.2500

22 005 307 00

57 5063 0069 8010 0090 0052 50

5AH45AS4A5R4GYA-BSU4GB5V4GA6AH66AK5W6AK66AL 5W

5 352 103 502 102 502 302 501 95I 80

60116SL7GT6SN7GTB6U8A12AT612AU612AV612BA612BA7

2 252 253 052001 901 90200

952 35

7815AL -GE 48 007815R 53 008122 120 008906AL 55 0015082 6 505728 CETRON 55 00807 290810 82 00812A 49 00

E F89 2 30 XG5-500 24 50 6A05A 1 75 128E6 200WE ALSO SUPPLYEF91 2 95 XRI-3200 72 50 6A05W 1 80 12BY7A 2 70

EF92EF93

2 20I 50

XRI-64000A2

120 00200

6AS66AS7G

2 40430

12BZ6I2DW7

3 703 75

EIMAC TUBES ANDACCESSORIES

1000-s of VALVES TRANSISTORS ICs IN STOCK. PLEASE ENOUIRE ON TYPES NOT LISTED.PRICES CORRECT AT TIME

BACKWARD WAVE OSCILL KLYSTRONS SOLID STATE REPLACEMENTS OF GOING TO PRESSCRTs MAGNETRONS THYRATRONS TERMS PLEASE ADD 01 .00IGNITRONS RECEIVING TUBE S TRANSMITTING TUBES P&P AND VAT 15°. to orders

ENTER 34 ON REPLY CA It I)

QuarthandOSCILLOSCOPESHP180A

HP18IA Storage mainframeTEK7603 Mount rome 100MHz,

PLUG -INS

HP1805AHP1825ATEK7A22 Dill AmplifierTEK7A26 Dual Trace Amp 200MHzTEK71353A Dual Tune Base

TEK 7880 Delayed Timebase 400MH/TEK 7685 Delaying Timebuse

400MHz

DVM'sDalton 1051 5' Digit AutorangingSolartron 1765Solomon 7065 6' : digitSolartron 7075Solartron 7050

VARIOUS TEST EQUIPMENTHP5345A Counter TimerHP3400A RMS VoltmeterHP5326A Counter TimerHP5370A Counter Tinier 100MHzFluke 895A Differential VoltmeterMarconi TF2162 Attenuator

0-111dBMarconi TF2430 Freq Counter 80MHzRural Dona 9500 Counter Timer

COMPUTERDEC 11/34A

DU II 03 D11/11-1, RX0IT.., 4051

WINCHESTER DRIVES 51/4"1.2J3 I uMb Full Freight ST506 (New> LI50£400 CORVUS 10MB/M for Apple £220

El 750 40MB Full Height Voice Coil Mos' 4036E45,7 Heads 40 mSec Average Access

£150

E150

£950L1400£1100

£950

11100

£650£350£750£500£450

£250C425

£175£225£200

£100£200£250

£575L600

11200

DAISY PRINTERSDiablo 630R0 SerialDiablo 630R0 Sheet FeederOlympia ESW3000 ParallelTEC Starwriter F10/40 (New) 12BitOlivetti PR430 Serial

£65(

El/'

£550£375

MATRIX PRINTERSTexas Silent 700 Serial 80 Col C125Texas Silent 800 Serial 132 Col C350Dec LA36 KSR Serial 132 Col £120Dec LA36 with Datosouth Board £l75Memorex 2073 Serial 80 Col £110A.1650 Ink Jet £120

PLOTTERS

HP722IC, HPIB, 8Pen A3 £875HP9872C £575HP9872S with Feed 8 Cutter C720Colcomp 1012 Serial 4 Pen L120

VDU'sTelevideo 925 £160Televideo 950 £220Pericom 7800 C125Pericom 6803 E125HP2624 with Thermal Printer £275HP2621 E150HP2647A Graphics Terminal £350

OPSU'sGould MGI2-10 Switch Mode £25Gould MG24-5 Switch Mode £25Gould Triple Output 15VI IA,

5V40A-12V4A £100

ENVIROMENTAL CHAMBER for component testing, etc - 55 to 200 (

ALL PRICES PLUS VAT AND CARRIAGE

£1,200

Ring Colin, 01-885 5522Unit 4, Hotspur Estate, West Road, Tottenham, London N17 OXJ.

QUALITY QUARTZCRYSTALS QUICKLY

FM P.0 Crystals

M.P.U Oscillators

I I I I I I10kHz 50kHz 100kHz 500kHz 1MHz 100MHzt Professional Crystals

Our frequency ranges are:

1.

We also supply quartz crystal filters.oscillators of all types andcommunication antennae.

Webster Electr.aicsILMINSTER. SOMERSET TA1990A. ENGLAND

TEL:10460157166 TELEX: 46571 FRONCY G

FAX (0460157865

I N TElt 37 ON REPLY CARD

250MHz 360MHz

6

.12_62--as ro

NEW! AFFORDABLEPCB CAD

O

FROMCHANNEL MICRO PRODUCTS LTD Maximum circuit board size greater than 2' x 2'. Powerful zoom facility and fast screen re -draw. Full on -screen editing. Mouse & Trackball compatible. Hard copy at 1:1, 2:1 & 4:1 from Epson F X or RX Plotter drivers for most popular plotters available. Low cost BBC Micro hardware keeps system cost below £1500.

Software only £240.

Please write or telephone for full details.

227 Canterbury Street, Gillingham, Kent ME7 5XB.Tel: 0634 570256 / 63228

ENTER HON REPLY ('AR I)


EN I Eli 2I ON REPLY C.XILD

75(1

Multimeter includestransistor andfrequency tests

testing and frequencymeasurement ranges are the lesscommon additional functions on anew multimeter. The Metex M3650offers a large I.c.d. with auto -zeroand a 30 -position range selectionswitch. The meter offers f.s.d.measurements of voltage up to 751)V.alternating: 1000V. direct: 20A director alternating current, resistancefrom 200 to 20%1 capacitancefrom 200pF to 20pLF and frequenciesup to 200kIlz. Crotech InstumentsLtd. 2 Stephenson Road. St. Ives.I Iuntingdon. Camhs. PE174WJ. Tel:0480 30181.

Two processors inoneArguments between engineers overwhether to use 6502 or 780 expertisein company projects are resolved atonce with Rockwell's dual processorchip. More seriously. the dualarchitecture c.p.u. combines the fasti/o handling of the 6502 architecturewith the versatile Hock moveinstructions of the Z8(1 onto onechip. the two processorscommunicating through tri-portram at locations 0020 on the 6502and FE00 on the 7.80. This ram is

accessible externally to allowmultiple dual c.p.us to he connectedtogether: bus contention arbitrationis executed with an algorithm thataccesses the tri-port ram to readpreset device numbers. To keep thenumber Of pins down the data bus ismultiplexed with the lower eight hitsof the address bus. leading to 32 pinsfor each c.p.u. rather than the moreusual 40. and the two-sided structurerequires an upper and a lower p.c.h.Rockwell's specialist single -chipdistributor is RCS Microsystems Ltd141 Uxbridge Road. Hampton Hill.Middx TW12 1BL. Tel: 01-9792294.

Sealed rechargeablebatteriesEight batteries have been added tothe Power -sonic range of sealed lead -acid batteries. The new versionsrange from an 80Ah 12V model downto a 500mAh 6V battery which is only58mm long.

The advantages of these batteriesis that they need no topping -up andcan he used in any position. Theyoffer leak -proof cases. suspendedelectrolyte. overcharge protection.cycle or float applications. highdischarge rate and extended shelflife. Power -Sonic Europe Ltd.Cornwallis I louse. !Inward Chase.Basildon. Essex SS14 31313. Tel: 0268293353.

Soft -centred controllerLatest in a series of innovativeproducts from Dallas Semiconductoris what they call a softmicrocontroller. Superficially theDS50110 resembles a c-mos 8051, hutthe package also contains an 8K or32K-hyte static ram 164K ispromised) and a ten-year lithiumbattery. These and some tricks builtinto the processor make the unitproof against power failure, whetherfor a few instants or for much longer.When the supply is restored theprocessor simply resumes executionfrom where is left off. with all dataand registers intact -a feature whichalso makes the device very suitable

for use in portable data gathering.Software updates can he

downloaded to the DS5000 fromremote sources, over the telephone ifneed he. The built-in memory can hepartitioned dynamically intoprogram and data areas by the user.

In addition, a software protectionfeature makes it possible to save andload programs in encrypted form. Ifan unauthorized user tries to resetthe lock hit. the 40 -hit keyword isautomatically erased.

Initial 1000 -off price of the12MI lz. 32K -byte version is $80.Details from Joseph Electronics inBirmingham on 021/64:16888.

REDUCEDSUBSCRIPTION

Make life easierand save moneyat the same timeby accepting our

offers ofreduced -pricesubscriptions.

'1

& WIRELESS WORLD

eal.tleneoh,. palette

Mobile radioupdate

V,h.f. voltage -controlledoscillator

A one-yearsubscription of £19.50brings 12 issues toyour door for the priceof 10, savirg nearly17% But for £53, youcan have a three-yearsubscription andsave nearly 25% -eight free issues.

And you won't have tokeep on ringing up to

ask forphotocopiesof articlesyou've

missed.

REDUCEDSUBSCRIPT

FORMIONORDERPlease send me Electronics

L_I & Wireless World for one yearat the special price of £19.50

Please send me Electronicsrn& Wireless World for three

years at the special price of £53.00' Inclusive of postage and packing.I enclose a cheque/PO to the valueof £made payable to Reed BusinessPublishing Limited.

Please debit my credit account.

Expiry date:El Access D BarclaycardNisa.0 Diners Club El American Express

Signed

Name

Job Title

Address

Please return to Electronics &Wireless World, Room 316.Quadrant House. The Quadrant.

Ltton, Surrey SM2 5AS.


low- cost logic analysisToday's digital circuitry can't be debugged with just a logic probe andoscilloscope. A logic analyser has become an essential tool.The Thurlby LA160 system puts logic analysis within the reach of everyengineer with a wide range of options to suit many different applications.

Prices from £395 plus vat16 or 32 data channels

IBM-PC interface options

Data pods for random logicPersonality modules for uPs

Microprocessor disassemblers

No other logic analyser system approaches the value for money of theThurlhy 1.A160. Contact us now for full technical data.

Illthurlbyi÷ Cambs.rig

Huntingdon,NTehwurlRboyaEdlescttrowneiscsLtd

designed and built in Britain PE17 4BG, England. Tel: (0480) 63570


Hitachi Oscilloscopes leading the way from C320in performance and pricing! +VAT

The highest yeah-)The Hitachi nam: is synonymous with quality and reliability andis hacked by a 2 s 2ar or 3 year warranty on every oscilloscope.The keenest pricing

ith prices startng at only. (320 for a 20N1H/ dual -trace modelHitachi's price -pt rformance ratio can not he bettered..1 he largest rangeNos% totalling If: models the Hitachi range covers bandwidthsfrom 20MH, to I 50M11/ and digital storage models to 60MH/.'The fastest set -s ice

e can supply any Hitachi 'scope immediately from stock and ssehack it ssith full calibration and after -sales service.

for colour brochu -e giving specifications and prices ring (04*)) 63570Ihtirll Electronics 1.Id., Ness Road, St. Ives, Cambs. PL I7 48(

ENTER 33 ON I? FPI v (' A RIl

EM S Power Systems

0

EMS manufactures DC Power Supplies andBattery Chargers both linear and switch modein a range from 5 VA to 3.2 KVA.Also a complete range of Standby, UPS andMains Stabilizer Systems 35 VA to 1 KVA. EMSspecialises in the manufacture of customisedproducts and has a full design anddevelopment facility.

EMS (Manufacturing) Limited,Chairborough Road,High Wycombe,Bucks HP12 3HH.Tel: (0494) 448484

Happy MemoriesPart type 1 off 25-99 100 up4164 150ns Not Texas 1.05 .95 .9041256 150ns 2.45 2.20 2.1041256 120ns 2.59 2.35 2.2541464 12Ons 3.35 2.99 2.792114 200ns Low Power 1.75 1.60 1.556116 150ns Low Power 1.40 1.25 1.206264 150ns Low Power 2.40 2.15 2.0562256 12Ons Low Power 8.75 8.50 8.252716 450ns 5 volt 2.95 2.85 2.802532 450ns 5.40 4.85 4.502732 450ns 2.60 2.40 2.252732A 250ns 3.30 2.85 2.752764 250ns Suit BBC 2.65 2.50 2.4027128 250ns Suit BBC 2.95 2.75 2.6527256 250ns 3.45 3.25 3.1027512 250ns 7.45 7.25 6.70Low profile IC sockets: Pins 8 14 16 18 20 24 28 40

Pence 5 9 10 11 12 15 17 24

Please ask for quote on higher quantities or items not shown.Data free on memories purchased, enquire cost for other.

Write or 'phone for list of other items including our 74LS seriesand a DISCOUNT ORDER FORM.

Please add 50p post & packing to orders under £15 andVAT to total. Access orders by 'phone or mail welcome.

Non -Military Government & Educational orderswelcome for minimum invoice value of £15 net.

HAPPY MEMORIES (WW),FREEPOST, Kington,

Herefordshire HR5 3BR.Tel: (054 422) 618

(No stamp required)

ENTER etti ON REPLY CARO

732

ENTER 17 ON REPLY CARO


rr

CROUCH 3132...

THE WISE DECISION

Can You Afford Less?

W

1 '41,11ft,A 1:31as -:4;64

isf

Eroiech Instruments LiaMed2 Stephenson Road, St. Ives, Huntingdon, Cambs. PE17 4WJ

IlinTelephone: (0480) 301818

The 3132 solves three requirements atone go. 1) 20MHz; 2 mV/div Dual TraceScope. 2) Triple DC P.S.U. + 5V; ± 12V(Floating common). 3) ComponentComparator, for comparing active andpassive compolents.

Ail for the price of a Scope.

£285 Exc. VAT & Delivery

Why pay a little less, for a lot less?

CAN YOU REALLY COPE WITHOUT OUR SCOPE ?

Just phone or write for your free copy of ourcatalogue.

ENTER 11 ON REPLY CA -it 11

Heard a,out RWC LTD yet? Looking for someone who speaksyour language? When it's radio we have something for everyone!

e supply Companies and Government Departments Worldwidewith Communications related systems and equipment. Some ofour specialities include: All mode Scanning Receivers and antennas 25 MHz - 2 GHz. Achoice of model and option modified by RWC to suit your exacting needsand requirements Custom designed Communication systems. UK MPT TypeApproved equipment designed to meet your requirements. includingBroadcast industry talkback systems. Handhelds. UHF/VHF repeatersystems. Marine Radio. HF point to point links, Radiotelephones andCellular telephones

Quality UK made Raycom hybrid modular VHF/UHF RF powerAmplifiers. 1-5w input all mode or class C units (RF switched) up to45W output

UK made Raycom Cost Effective Regulated 13.8 Volt powersupplies. A choice of units 3A to 12A with metered options

Raycom UK made Land mobile VHF/UHF antennas. A choice of5/8 whips. UHF colinears and 1/4 wave whips in the range 50-950MHzwith a choice of bases and magnetic mounts to suit modernrequirements

New and second user Amateur and Business Radio Main brandHF/VHF/UHF transceivers, receivers and accessories. Weproduce modification kits to improve and expand facilities and offerguaranteed used equipment checked to original specification As for ourbi-weekly used list

RF semiconductors and RF Power Modules for HF/VHF/UHF. Arange imported and European made specialist devices for OEM and theservice industry Try us for fast service and delivery

We offer the largest selection of Radio allied services underone roof

Call us by Telephone. Telex or FAX for more details, or send us a detailedspecification of your needs for a fast written Quotation

Export enquiries invited.\me Tel: 021 421 8201 (zee mswerreansi

Telex: 134303 G TXAGWM

ENTER 21 ON RU:PLY CARO

FOR THE BEST CIRCUITSIMULATION C.A.D.Designers are turning to 'THOSE ENGINEERS' software. They keep aheadby knowing what is going on while free to experiment without the costs.delays and uncertainties of physical testing. Those Engineers softwarewhich creates a net list removes the chores and errors in documenting.Ask us too for schematic layout software.

Features:

%net, Diode Oscf Rata,

CC Transfer Curve

ECA-2 is an example of one of our circuit simulators

Transient analysis -DC analysis -AC analysis

Fourier analysis -Tolerancing -Temperature

Non -I near simulation -Full mode model -Complex components -Variants -

Macro models -

Probe -

Dual mode -

High capacity -

High SpeedReference Manual -

No risk trial -

Low price -

timing diagrams plotted.DC transfer curves plotted.Bode curves (gain and phase) plotted.also phase delay output.transients output in frequency domainMonte Carlo and Worst Case.Components temperature effectssupportedBreakpoints and polynominals supportedI - lo* (expffv'q)/(n'k't)) -Resistors may have inductance etc. etc.Component characteristics can be made tovary with both time and frequencyaccording to any function. Offset currentsmay be imposed.Up to 64 connections per model to maincircuit, no limit on number or size.Signals may be sampled or injectedanywhere.Interactive mode has powerful editing andinterrupting facilities Batch mode forheavy work allows you to come back.Sparse matrix technique allows typicallyover 500 modes in 5I2K memory. 8087 (or80287) coprocessors supported.A ring -bound reference manual of over 200pages is an integral part of ECA-2.If you need more convincing, ring us fordetails of money -back trialECA-2 costs lust 1695 k VAT. ECA-2compares favourably with well-knownmainframe simulators and is more powerfulthan any other we know available on PCs

THOSE ENGINEERS software which is available from C99 supports IBM PC s andompatibles and the range of BBC microcomputers. As engineers in electronic and

,iechanical product and process design, we welcome enquiries for other requirements.

THOSE ENGINEERS LTD. Sales: 106a Fortune Green Road.West Hampstead. London NW6 1DS.Tel 01.435 2771. Telex 8950511 mark for mailbox 23332001.

ENTER :19 ON ItEP1.1( ('ARt)

ELECTRONICS & WIRELESS WORLD 75:1

I0 BROADCASTDigits-not

without tearsDigital audio is rapidly infiltrat-ing into both radio and televisionbroadcasting, although not with-out experiencing difficulties sel-dom foreseen by the early advo-cates of "rugged go/no-go,hands-off operation." Indeed, itis the abrupt change from go tono-go, that replaces the more -certain but more -gradual de-gradation of analogue signals,that is tending to cause unex-pected headaches for transmis-sion engineers. British Telecomengineers have reported en-countering unexpectedly severeproblems during the rare occa-sions when multipathtropospheric -propagation condi-tions exist right down to thelevels of microwave towers.

In an ICAP87 paper, M.C.D.Maddocks and J.H. Stott of BBCResearch describe problems ex-perienced on a new digital u.h.f.link between Stockland Hill,Devon and Alderney intended tocarry a multiplex of radio prog-rammes from the UK to theChannel Islands radio transmit-ters, replacing existing analoguelinks. This was designed to pro-vide reliable, high -quality audio,despite there being at least a50dB fading range on this long,over -the -horizon sea path. Pro-pagation data were availablefrom the existing analogue tele-vision links over this path, re-ceived on the IBA's adaptiveantenna and (for diversity) a

large parabolic dish reflectorantenna.

Predictions suggested thatsignal-to-noise values should besufficient for the digital link to beopen for 99.85 per cent of thetime, free of objectionable co -channel interference 99.7 percent of the time, indicating atotal predicted performance of99.55 per cent of time and a linkoperational time of 99.4 per cent.In practice, measurements onthe experimental link taken overseveral months indicated a linkoperational time of 97.8 per centwith 89.5 per cent error -freeseconds.

The BBC engineers noted thatalthough the majority of linkfailures lasted less than tenseconds, there were a significantnumber of longer failures, sub-jectively more damaging and in-

creasing in frequency in earlyafternoon and late -night periods,both recognised as importantradio broadcasting times. Thelink failures also posed the prob-lem that they were neither soshort as to be disguised in thesignal decoding, for example bymuting, nor so long as to be veryrare. While it is hoped to identifythe reasons for the unexpectedlypoor performance of the ex-perimental link, it seems likelythat a considerably more com-plex digital modem may provenecessary. No doubt all will comeright in the end but it is anotherindication that digital transmis-sion can throw up new problems.

Digitalbroadcasting

Some years ago the BBC con-ducted a programme of ex-perimental terrestrial broadcast-ing of digital signals using theBand 1 v.h.f. transmitter at Pon -top Pike. Although this wasfound to provide excellent quali-ty reception at most, though notall. domestic locations, portableand mobile reception proved ex-tremely dicey owing to the des-tructive effects of short-termmultipath propagation -a condi-tion that can still cause digitalteletext to display "garbage"(error -prone) pages in someurban standing -wave situations.But teletext is not expected tohave to cope often with the se-vere multipath of mobile recep-tion.

Although both the BBC andIBA are planning to use digitalstereo (plus the conventionalanalogue channel) for televisionsound in the fairly near future,direct transmission of signals indigital form for terrestrial radiobroadcasting in the UK seems tohave been put on the back -burner for the time being.

However, according to theRussian engineer F.I. Vlasov in a1986 article in the OIRT journalRadio and Television. an ex-perimental digital sound broad-casting system was established in1983 in Leningrad. and then in1985 in both Leningrad and Tal-lin using the "newly available"frequency of 102.656 -MHz (untilrecently East European v.h.f.broadcasting has tended to usefrequencies around 70 MHz). No

details are given of the resultsachieved and the extent of anymultipath problems but it is sug-gested that while the band 100 to108 MHz would be suitable foronly three analogue stereo net-works. six stereo digital pro-grammes could be accommo-dated as a multiplex within a4 -MHz band, provided that alltransmitters used the same car-rier frequency and each soundsignal (mono or one of a stereo -pair) is coded in a floating-pointcode with 10 -bit mantissa and3 -level codes. With a samplingfrequency of 32 kHz, the bit -ratewould be 4.096 Mbit/s with dou-ble phase -shift modulation.

F.I. Vlasov concludes that "atthe present time we are partici-pating in a revolutionary processof a radical change in soundbroadcasting technology. Digitalsound engineering is the tech-nology of the 21st century: in ourdays it is making its first stepsand conquering ever new fields."

It is clear from this paper thatthe Russian engineers are care-fully following developments indigital audio engineering outsideof the USSR. F.I. Vlasov regretsthat standardization of encodingparameters has not beenachieved with 48 kHz samplingused in digital studios. 44.1 kHzfor laser (CD) sound, and 32 kHzfor transmission links, with re-peated rate -conversions increas-ing costs and, unless adequatemeasures are taken, reducingthe quality of programme sound.Bit numbers and coding lawsalso differ: 16 bit linear codinghas been standardized for CD.but 14 bit linear and 10 and 9.5bit non-linear codes are used ontransmission channels. Everyattempt, he believes, should bemade to avoid increasing stillfurther the divergence betweencoding parameters.

He notes that CD records havecreated a need for improved re-production systems and lists assuitable for monitoring purposesanalogue loudspeakers havingabout 110 dB dynamic range andcapable of maximum soundpressure levels of about 128 dB.in which category he puts theTechnics B-10. Mitsubishi DS -505 and Junior (Kreisler) louds-peakers, adding "The monitorunits of the English firms Tan-noy (M-1000 and M-3000 units)and Bowers & Wilkins (B&W-801and B&W-868) also approach

meeting the requirements ofdigital."

But he also looks beyond theanalogue systems, noting thatBell Laboratories have developeda system for immediate conver-sion of a digital signal with thedecoding effected directly on thediaphragm. As a third possibilityhe notes the potential of adaptivesystems such as that demons-trated by Acoustical Research in1982 which includes adaptationto the acoustic characteristics ofthe listening room by the use ofmicroprocessors, adding "In ouropinion the development ofadaptive sound reproduction sys-tems constitutes the main trendof development in the near fu-ture, as it will be possible tocreate sound reproduction sys-tems satisfying all requirementsof the prospective digital soundchannel."

Databroadcasting

The use of digital data carried onsub -carriers of v.h.f. broadcaststations seems likely to increasein the near future. Telerate (UK)Ltd have now launched theirsubscriber radio teletext serviceon the 97.3 MHz LBC channel inLondon, with the similar Tele-met system on the Capital trans-mitter due later this year. TheBBC has launched full test trans-missions of the EBU Radio DataService (RDS) in preparation foran official launch of the systemin September. providing auto-matic location of the strongestsignal. display of station name.alternative frequencies of a givenservice, time and date. This ser-vice is due to be available from allBBC v.h.f. transmitters in Eng-land by the autumn, and RDSmay also soon be available on IBAtransmitters. The successful in-troduction depends to a markedextent upon the willingness ofsemiconductor manufacturersto develop special purpose I.s.i.chips. with the usual chicken -and -egg quandary of firms beingreluctant to incur heavy develop-ment costs until they have someevidence of a market demand:while broadcasters find it diffi-cult to start a new service untilreceivers are available.

Radio Broadcast is written by PatHawker.


KADIO COMMUNICATIONSPackets on the

moveWhile the Royal Signals are stillstriving to come to terms withorganizational and managementrequirements for the Ptarmigantactical Cil line and radio battle-field communications system, ateam at the Royal Signals &Radar Establishment at Malvernhas been busy investigating thepossibility of introducing store -and -forward digital packet -switching technology into com-bat net radio systems operatingon a single narrow -band chan-nel. Following the use of a smallnumber of experimental units,the team intends to expand itswork with the acquisition bycommercial procurement of anexperimental 25 station unit.With this, it is planned to developand further refine the distributedalgorithms so far developedbased on the need for the packetswitching to operate effectivelyin a highly mobile and hostileenvironment.

The current RSRE work isdescribed by B.H. and T.R.Davies in some detail in an in-vited paper in a special issue(January, 1987) of Proc. IEEE.This issue devotes over 150 pagesto the use of packet -switchingtechnology for mobile -radio net-works, mostly for military -typeapplications. The guest editorsapologize for the preponderanceof military -sponsored papers, ex-plaining "This is due to the un-fortunate lack of success that weexperienced in including a paperon the application of this tech-nology to the commerical andamateur sectors. This absence.however, should not underminethe importance of these areas ofapplications. In fact, some com-mercial systems are in use. in-cluding communications to fieldengineers and support of pack-age delivery services."

Meanwhile, the UK Royal Sig-nals officers are still seeking tolearn from early field experienceof Ptarmigan and its radio -relaysector, Treffid, following its rolein the 1986 "Exercise SummerSales" in West Germany. whichwitnessed the first large-scaleuse of Ptarmigan at Corps level.

It is recognised that the RoyalSignals faces the challenge ofmanaging an area system super-imposed on a hierarchical corn-

mand structure, a friction -provoking situation that is notproving easy to solve. Major G.R.Leach has written (J. Royal Sig-nals Institution) "successful de-ployment of Ptarmigan relies ona close understanding of the dif-ference between command of thetrunk system and its electronicmanagements." He stresses thatthe success of Ptarmigan is re-liant on good -quality radio -relaylinks and that the burden ofproviding these depends on theability of junior commanders,including the radio -relay detach-ment commanders, the Reccesergeants and the trunk -networkcommanders. Differences ofopinion between these on suchmatters as the siting of the radio -relay units can jeopardize theeffective operation of a wholePtarmigan battlefield system.

Such large-scale military exer-cises are having increasingly torecognise that Warsaw Pactforces have developed a sophisti-cated concept of offensive elec-tronic warfare (radio electroniccombat support) and would cer-tainly attempt to intercept, ex-ploit and disrupt the com-munications of their enemy.

Supercooldiodes?

The recent marked upsurge ofR&D interest in superconductiv-ity has followed the discovery,initially by Bednorz and Miller ofIBM Zurich but now apparentlywith Japanese scientists in thelead. of a completely new familyof "high -temperature" oxide -ceramic superconductors andseen by some observers as "aninvention comparable to that ofthe transistor." For the com-munications engineers, it raisesthe possibility of improved low -noise devices for microwave,millimetre -wave and opticalcommunications. The way seemsopen for improved diode detec-tors and mixers by means ofsuper -Schottky diodes withjunctions having a hybridsuperconductor/semiconductorstructure used with the relativelyinexpensive liquid nitrogencoolant.

Superconductivity. first dis-covered by the Dutch physicistHeike Kamerlingh-Onnes in1911. is the curious property of

many electrical conductors tochange abruptly to a state of nomeasurable resistance whentheir temperature closelyapproaches absolute zero (OK.-273°C). It was not until 1957that a comprehensive theory ofsuperconductivity was formu-lated by J. Bardeen, L.N. Cooperand J.R. Schrieffer (the "BCS"theory). This led to a graduallyincreasing exploitation, or atleast investigations into themany potential applications inthe 1960s, including the con-firmation of some aspects of the"Josephson effect" predicted byBrian Josephson in 1962 andwhich is seen as providing thekey to the application of super-conductivity for super -fast com-puters as well as for low -noiseelectronics.

Most of the R&D on theJosephson effect has been target-ted on the development of com-puters. with IBM concentratingon its use as a switching device(though reportedly largely aban-doning this project a few yearsago) and Bell Laboratories seek-ing ways of using Josephsonjunctions to increase the speedand capacity of central computermemories.

But until the recent ceramic -oxide breakthrough, supercon-ductivity could only he achievedwith the use of costly ('.quidhelium (boiling point 4K) as thecoolant. With the transition to asuperconductive state of barium -yttrium -copper oxide found byMitsubishi scientists to be over90K, the much cheaper andeasier to handle liquid nitrogen(boiling point 77K) can be usedas the coolant.

It could, however, be low -noise communications that maybenefit before computers.Temperature of the coolant is

not the only problem in usingJosephson -junction devices incomputers. It has yet to beshown that it is possible to com-bine large numbers of such de-vices on to a single chip, becauseof the tendency for different sta-bility problems to be found ineach junction. This, however.would not necessarily preventtheir use as discrete devices inlow -noise applications. NEChave reported the developmentof a functioning Josephson de-vice based on two layers ofsingle-phase yttr um -bariumcopper oxide.

It may be recalled that theoriginal low -noise receiver atCoonhilly Downs in the early1960s was based on a helium -cooled maser having extremelylow -noise parameters but, apartfrom expense, this proved tohave too narrow a bandwidth forthe later generations of com-munications satellites.

ICAP87Among the near -950 pages of the(EE's two-part Conference BookNo 274 covering the recent In-ternational Conference onAntennas and Propagation(ICAP87) at Sheffield Universityare no less than 179 papers and47 poster presentations - for-midable tomes indeed. However,they include not only the usualesoteric and highly mathematic-al analyses favoured by special-ists in these fields but also quite anumber of more down-to-earth(if that is the appropriate ex-pression) and practical papers.These range from interestinghistorical surveys of 100 years(dating from Heinrich Hertz) ofantenna development and pro-pagation research to practicalengineering papers on the designof microwave towers with emph-asis on wind hazards. The BBChas also come up with somelessons from the past, includingexplanations of how they tackledsuch unexpected problems as thePenge effect. "ghosts" in Pre-ston. hazard -lamp hazards andthe rusty -bolt effect that can giverise to spurious inter -modulation products. It is alsointeresting to note that MarconiResearch have been doing newdesign work on the 50 -year -plusBruce rhombic antenna relatingbandwidth to apex angle. Recep-tion of v.h.f. signals in urbanareas, including an improvedSwedish model for hilly wood-land from which it seems that aforest may theorectically be tre-ated as a dissipative. lossy dielec-tric slab lying on a half -spaceground. There is also an illumi-nating paper on height -gain atv.h.f. in urban, rural and over -sea paths. The computer hasmade possible the use of the"Method of Moment" techniqueto predict antenna performance.

Radio Communications is writ-ten M' Pat Harker.


GET TO THECORE

OF COMPACTPOWER SUPPLY

NUVOTEMCUSTOM -DESIGNED

COMPONENTSTheir compact size and low magnetic

interference make Nuvotem's toroidal transformersideal for today's types of power supply and powerrequirements in a wide variety of electronicapplications. The benefits are clear: Significant savings in weight and volume overconventional transformers. Competitive price. No air gaps - hum almost completely eliminated. Nuvotem design and advisory service -customised components for specific applications. Highest standards of quality assurance - 100°/0tested. Also available - a standard range - 15VA-500VAplus a range of filter chokes.

GET TOME CORE OF THINGS -for further information complete and return the couponor telephone Nuvotem today.=NEM, 41/M ILM7

NamePositionCompanyAddress

TelephoneNuvotem TeorantaCrony. Co. DonegalIrelandTel: Int. +353+75+21177/48139Telex: 42123 NUVO ElA member Of Taler333 CI' ' (Ar 411


Used equipment - with 30 days guarantee. Manuals supplied if possible. This is a verysmall sample of stock. SAE or telephone for LISTS. Please check availability before

ordering. Carria,;e all units f 16. VAT to be added to total on Goods and Carriage.

OSCILLOSCOPE BARGAIN

ONLY LAI5 each

SPECIAL OFFERS

OSCILLOSCOPESL2.50041.500

. 4120041.200

490045504325432542501200

L165i 4100

411015034225

COMMUNICATION RECEIVERS' ' ...- 0 ''

MULTIMETERS445l

465

45

LIO

'. L1200 each BRUEL & KJOER EQUIPMENT£3500it cooL3000

Hetes 0, r rr. Ar 0. c ' .0e.' I I 750Lew, Rec tarter Type :10/ L1400&al Frequency Osr Hato, 1,0 £400

GENERATORS

£950L1200

nr000

/500f.,35°x.'.'1°2

0. -,

DISK DRIVE X5112409 In SI/ I 64 & 128 I 54 Out SueW25rtan 110 e..QWERTY KEYBOARD (as c LYNX MICRO) Push tr 0,0.0Cased '4 , !seaSWITCHED MODE PSU . 129 0 254. 5V ISA ..: . ::.07.p 13 L30 eat M1

8,1009 .100, -.V t ..' .010101. .1 11 L150 each

1500

L2001150

440475

41504100

4609500

£504400

NEW EQUIPMENT,Ayi G ()SCUM" ' ....,.. Delay Seep

1543

1314

'0 h STAN WOW I WIRS (p&p 151.,. .1.0 IU- I 001.1147 RatrorPerqdlcre rnterval etc 1219APO. i 0 100- I 00MHr 'As above rell, more luncloml 1285HL ACK STAR FREQUENCY COUNTERS (p&p 441 Meteor100-100MH7 L99Meteor 600-600MHz £126Meteor 1000 -ION/ 4175BLACK STAR JUF1TOR 500 FUNCTION GENERATOR So, r -,rongle 0 1Hz-50010-It toap 141 £110'10,115 rl. Ot P ,IAR .1'11 RA' 0R 1,110 Nod. 4199

43 000

11 750

4850

ISOLATING TRANSFORMERS 240V Input

IA

I.ind held 28 me, ,r,

439 5013350

II I

STEWART OF READINGREADING,

Telephone: 0734 68041.lilr 110 WYKENAM ROAD, BERKS RG6 1PL

MON-FRI. (UNTIL 8pm. THURS)Callers welcome 9am to 5.30pm.


1 KESTREL ELECTRONICCOMPONENTS LTD.

All items guaranteed to manufacturers spec.. Many other items available.

'Exclusive of V.A.T. and Post and Package'50 50 1. 50

74LS00 013 0 10 6821 1 40 1 00 2764-25 2 40 2.2074LSO4 0 13 010 6502 330 280 27128-25 3.50 3 4074LS08 0 13 0 10 6522 330 2 80 27256-25 390 3 7074LS21 0 15 0 12 65CO2 700 600 6116LP-3 1 50 1 4074LS37 0 13 0 10 6809P 3 20 285 6264LP-15 200 1 8574LS74 0.13 0.10 745138 0.30 0 25 62256-12 11 00 9.5074LS86 0.13 0 10 74S240 0 40 0 35 4164-15 1 00 aso74LS122 020 0 18 8085A 1 40 1.20 41256-15 240 22074LS244 040 0.32 8255-5 1.80 1 65 Z8OACPU 140 1 0074LS245 0.44 032 4 meg Crystal 030 0 25 280ACTC 1 40 1 CO74LS367 0 23 017 LM324 0 25 020 ZEIOAP10 1 40 1 1074LS373 0 40 030 LM339 0.25 020 8253 1 40 1 2574LS374 0 40 0.34 LM386 050 042 6845 1 90 1 3074LS399 0 30 020 LM556 035 025

All memory prices are fluctuating daily please phone to confirm prices.

178 Brighton Road,Purley, Surrey CR2 4HATel: 01-668 7522


Editorial Feature ListAUGUST 1987Short -haul optical -fibre data communica-tions is an essential part of modern communica-tions systems This feature presents an overviewof the techniques employed and the hardwareavailable.SEPTEMBER 1987Microwave semiconductor devices. Thesespecialised components retain an air of mysteryfor many engineers. We present a feature on thephysics of these devices and characterize thetypes now is use.For further advertising details please ringMartin Perry on: 661 3130 or Michael Downing on 661 8640


-TELEVISION BROADCASTSystems

proliferateAt the height of the PAL \ TSC/SECAM controversy in the1960s, at least one large orga-nization issued a firm edict thatits engineers should not attemptto develop any new colour -encoding systems, but insteadshould concentrate on solvingthe problems of one of the threeproposed systems which wereshowing an alarming tendencyto proliferate new versions.Judging by the number of sys-tems now emerging in the fieldof direct -broadcasting fromsatellite and for wide-screenh.d.tv. perhaps it is time that asimilar ban should be imposed.The basic problem is to decidewhether "compatibility" with ex-isting standards is or is not anessential requirement for possi-ble world standards.

There is at least still time forconsideration, with Americanbroadcasters at the momentmore concerned with financialthan engineering aspects of fu-ture television, partly resultingfrom the financial difficultiesthat have followed companytake-overs or from fighting offsuch take-overs. in which theprocess of issuing "junk bonds"seems to have led to over-capitalization and sparked off adrastic round of cost-cutting. Yetthe increasing practice of usingelectronic production ratherthan film for some of the majorAmerican drama series and sub-sequent up -conversion to 625lines does underline the need foran improved electronic produc-tion standard, whether or notthis is the 1125 -line 60Hz stan-dard that has been opposed byEuropean broadcasters.(although German broadcasters.but not the German Bundespost,have committed themselves tosupport of 1125 as a productionstandard).

William Dobbie of BritishTelecom Research is proposing anew MAC system, designed foroptimum bandwidth efficiency.which would allow two program-mes of conventional quality to betransmitted in a single DBSchannel, or alternatively wouldprovide options for a single wide-screen h.d.tv transmission. Inthe USA, Faroudja Laboratorieshave developed a technique for

improving the images of 525 -lineNTSC. Dr William Glenn is advo-cating an h.d.tv system compati-ble with NTSC which could betransmitted with the aid of anextra 3MHz channel on terrest-rial networks. Richard Iredale(Del Ray Group) has a proposedHD-NTSC system that would befully compatible, depends on a"TriScan" concept of smart scan-ning combined with digital pro-cessing in the receiver and wouldpermit a change of aspect ratio to14:9. Europe is still divided be-tween support for the MAC varia-tions including B -MAC. C -MAC.D -MAC (Eu-MAC ), D2 -MAC etc..with subsequent "evolutionary"progress to wide-screen h.d.tv.

Sellingtechnology

1986 was a boom year for theHigh Street consumer -electronics shops, with no lessthan 3.9 million colour televi-sion sets reaching the retailersand rental chains: with video-cassette recorders recovering tothe 2 million levels achieved afew years ago: and with CD re-cord players up fourfold on 1985to almost 640,000 units deli-vered to the trade. With so manymajor Japanese firms now hav-ing UK factories it is also notsurprising that exports of theso-called "brown goods" are alsorunning at record figures.

But the retail trade is far fromhappy. claiming that profit mar-gins are far too low. Lord Chap -pie, chairman of BREMA. claims"I find it depressing that such anefficient and dynamic industryfinds it impossible to hold pricesat sensible levels which wouldallow reasonable margins to allinvolved." This reflects the rowthat broke out following anannouncement earlier this yearthat some manufacturers werebeginning to cut the £50 -or -soprice differential between setsfitted with the flatter, squarerpicture tubes. now amounting toabout 70 per cent of the produc-tion of large -screen sets. andthose with conventionallyshaped picture tubes.

The BREMA chairman be-lieves that technological innova-tion should be used to induce thepublic to pay "more reasonable"prices. quoting the example of

teletext. Yet my recollection ofthe early struggle to establishteletext as a viable operation isthat it nearly died the death ofpublic apathy until the Depart-ment of Trade & Industry step-ped in, appointed R:c Foot topromote the system energetical-ly and induce the Treasury tomake, at least temporarily,financial concessions that en-abled rental firms to charge vir-tually the same rentals as forremote -controlled sets not fittedwith teletext decoders.

Then again, BSB. in planningto begin direct broadcastingfrom satellite by 1980, havewidely publicized the figure of£200 as the likely "initial" cost ofa suitable dish antenna plus theindoor unit including the MACdecoder, a decidedly optimisticfigure that would not give muchscope for "sensible margins".especially if the public came toexpect that this would includeinstallation costs.

Apart from the controversialdigital audio recorders (DAT)which may finally appear in HighStreet shops later this year.another potential market thathas yet to be developed is forconsumer -priced electronic"stills" cameras. Casio haveannounced that they hope tolaunch the first such cameraintended specifically for the con-sumer in the North Americanmarket very shortly. This camerauses the standard 2 -in video -floppy as standardized for profes-sional cameras. This can hold upto 25 full frames or 50 fields ofcolour pictures. The Casiocamera has an m.o.s. image sen-sor capable of 280.000 -pixel re-solution, shutter speeds fromone -eighth to one -thousandth ofa second and the ability to takefive fields continuously in onesecond. The camera will includethe facility to playback on anytelevision set 1525 -line models)without the need for a separateplayer unit.

The price in Japan is Tinder£500.

Puzzles remainThe publication last November.coinciding with the many 50 -year anniversary events, of the500 -page hook British Television- The Formative Years. by Pro-fessor R.W. Burns - was clearly

intended, and seems likely toremain, the definitive study ofBritish television from the firstBaird experiments in 1923 to theconfirmation of the Marconi -EMI 405 -line system as the UKstandard for Alexandra Palace inFebruary 1937. It covers in con-siderable detail the 1926 to 1934struggle by Baird to make 30 -linetelevision broadcasting the basisof a viable industry, against thewell-founded opposition of theBBC. At first the BBC were sup-ported in opposing Baird by thePost Office engineers, who alsoformed the executive side of theregulatory body. But then, fol-lowing the success of Baird inobtaining political support andthe belief of the Post Office'slegal advisors that the then Wire-less Telegraphy Acts did not cov-er the transmission of visualimages, the Post Office attitudebecame increasingly ambivalentand in the end they virtuallyforced the BBC, albeit reluctant-ly, to agree to provide transmit-ters for experimental 30 -linetransmissions.

Professor Burns has drawnwidely, although at times ratherselectively. upon the BBC andPost Office archives. But I won-der if I am alone in feeling that hehas left a few important ques-tions unaswered.

For example, how did Profes-sor E. Taylor Jones come to writesuch an extraordinarily favour-able report in the highly re-spected journal Nature (18 June.1927) of the crude London/Glasgow land -line demonstra-tions, writing "The image wasperfectly steady in position, wasremarkably free from distortionand showed no sign of thestreakiness which was. I believe,in evidence in the earlier ex-periments...My impression afterwitnessing these demonstrationsis that the chief difficulties con-nected with television have beenovercome by Mr Baird and thatthe improvements still to beeffected are mainly matters ofdetail." It is extremely difficult tobelieve that this support fairlyrepresented genuine resultsachieved in these hurriedly setup 1927 demonstrations. WasProfessor Jones fooled? And if sowho was responsible for "rig-ging" the demonstration?

Television Broadcast is writtenby Pat Hawker.


01-208 1177 rh( 1-INOMA VIC L D 01-208 1177BBC Computer & Econet Referral Centre

AME115 BBC MASTER1 tree software £385 fa) AMB12 BBC MASTER Econet 0299 (a)AMCO6 Turbo (65C - 021 E xpansion Module 199(b)ADC06 512 Processor 1195(b) ADJ24 Advanced Ret Manual C113(c)ADF14 Rom Caendge £12.75 (b) ADJ23 Ref Manual Part II £14 fa)ADJ22 Ref Manual Part 1 C14 (e) BBC Master Dust Cover C4.75 (d)

BBC MASTER COMPACTFree bundled software within priceSYSTEM I 128K Single 640K Once and bundled software £385 (a)SYSTEM 2 System 1 with a 12 Hi Res RGB Monitor E469 (a)SYSTEM 3 ystem 1 with a 14 Med Res RGB Monitor £599 fa)Second 3 5 Drive Ka C99 (c) Extension Cable for ext 5 25 drive C10 (d)

View 3.0 User Guide C10 (d)BBC Dust Cover C4.5008ADFS ROM (for 13 with 1770 DFS 5 B Plus C26 (d)ACORN 280 2nd Processors C329 (a)MULTIFORM Z80 2nd Processor £269 (b)TORCH Z80 2nd Processor ZEP 100TZDP 240 ZEP 100 with Technomatic PD800P dual drive with built-i

Viewsheet User Guide C10 (d)1770 DFS Upgrade for Model B C43 (41)

1 20S ROM EIS (d)Universal 2nd Processor Adaptor C75 (b)

ACORN IEEE interlace 1265 (a)C229 (a)

n monitor stand £439 (a)

META Version III - The only package available in the micro market that willassemble 27 different processors at the price offered. Supplied on two 16Kroms and two discs and fully compatible with all BBC models. Please phonefor comprehensive leaflet £145 (b).

We stock the full range of ACORN hardware and firmware and a very wide range of otherperipherals for the BBC For detailed specifications and pricing please send for our leaflet

DISC5.25" Single Drives 40/50 switchable:

DRIVESTS400 400K/640K £114 (b)PS400 400K/640K with integral mains power supply £129 (b)5.25" Dual Drives 40/80 switchable:TD800 800101208K £226(a)PD800 800/K1280K with integral mains powr supply £229 (a)PD800P 800K/1280K with integral mains power supply and monitor stand £249 (a)3.5" 80T DS Drives:TS351 Single 400K/640K 175 (b)PS351 Single 400K/640K with integral mains power supply £95 (b)TD352 Dual 800K/1280K f135 (b)P0352 Dual 800K/' 280K with integral mains power supply 1152 (b)PD853 Combo Dual 5.25'73.5" drive with p.s.0 £229 (a)

EPSONEPSONFX800FX1000EX800EX 1000L0800 (80 col)L01000L02500

PRINTERS & PLOTTERSSTAR Nl_10 (Parallel Interface) £229 (a)

BROTHER HR20 £349 (a)

COLOUR PRINTERSIntegrex Jet Printer 1549 (a)

Dotprint Plus NLO Rom forTAXAN Epson versions for FX, RX. MXKP815 (160 cps) £249 (a) and GLP £28 (d)

£329 (a)£449 (a)£409 (a)£595 (a)£439 (a)£609 (a)£795 (a)

KP915 (180 cps) 1379(a)

JUKI6100 (Daisy Wheel)

PLOTTERSHitachi 672 1479 (a)Graphics Workstation

(A3 Plotter) 1599 (a)NATIONAL PANASONIC Plotmate A4S £375 (a)KX P 1081 (80 col) 1169 (a) Plotmate A4SM £455 (a)KX P 3131 (38K butter) £249 (a) Plotmate A3 £425 (a)KX P 3132 (32K butler) £249 (a) Plotmate A3M £574 (a)

£310 (a)

3M FLOPPY DISCSIndustry Standard floppy discs with a lifetime guarantee. Discs in packs of 10

51/4" Discs 31/2" Discs40 T SS DD 110.00(d) 40 T DS DD 111.50(`d) 80 T DS DD £18.0080 T SS DD 114.00 (d) 80 T DS OD 115.00 (d) 80 T DS DD £23.00

FLOPPICLENE DRIVEHEAD CLEANING KITFLOPPICLENE Disc Head Cleaning Kit with 28 disposable cleaning discsensures continued optimum performance of the drives. 5' 4" £12.50 (d)

3' 2" £14.00 (d)

DRIVE ACCESSORIESSingle Disc Cable E6 (d) Dual Disc Cable £8.50 (d)10 Disc Library Case £1.80 (d) 30 x 5' :2 Disc Storage Box E6 (c)50 x 512 Disc Lockable Box 09.00 (c) 1130 x 512' Disc Lockable Box E13 (c)

PRINTER ACCESSORIESWe hold a wide range of printer attachments (sheet feeders, tractor feeds etc)

i in stock. Serial, parallel, IEEE and other interfaces also available. Ribbonsavailable for all above plotters. Pens with a variety of tips and colours alsoavailable. Please phone for details and prices.Plain Fanfold Paper with extra fine perforation (Clean Edge):2000 sheets 9 5' x 11" 113(b) 2000 sheets 14.5' x 11' £18.50(b)Labels per 1000s Single Row 3:" x 1 7/16' 15.25(d) Triple Row 2-7/16' x 1 7/16" 15.00(d)

MONITORSRGB 14"1431 Std Res E179 (a)1451 Med Res 1225 (a)1441 Hi Res 1365 (a)MICROVITEC 14" RGB/PAL/Audio1431AP Std Res 1199 (a)1451AP Std Res £259 (a)All above monitors available in plastic ormetal case.MICROVITEC 2e2030CS RGB/PAL'Aucho £380 (a)2040CS RGB/PAL'Aduto £685 (a)TAXANK12SV 62012" 1279 (a)K12SV 62512" £319 (a)MITSUBISHIXG1404 14 Med Res RGB, IBM i3 BBCcompatible 1219 (a)

MONOCHROMETAXAS 12 HI-RESKX117 12 Green P31 185(aKX118 12" P39 £95(aKX119 12' Amber £90 (a

PHILIPS 12" HI-RESBM7502 green screen E75 (a)BM7522 amber screen 179 (a)

ACCESSORIESMicrovitec Swivel Base (DS4 only) E20 (C)Taxan Mono Swivel Base withcl°Ck£22 (c)Phipps Swivel Base £14 (c)BBC RGB Cable 15 (d)

13.50 (d)MicrovitecTaxan 15 (d) Monochrome 13.50 (d)Touchtec - 501 £219 (b)

MODEMSAll modems carry a full BT approval

MIRACLE TECHNOLOGY WS Range

WS4000 V21/V23 (Hayes Compatible.Intelligent, Auto Dial/Auto Answer) £149 (b)WS3000 V21/23 Professional As WS4000and with BELL standards and battery back upfor memory £265 (b)

WS3000 V22 Professional As WS300 V21/23but with 1200 baud full duplex 1445 (b)

WS3000 V22 Ws Professional As V22 and2400 baud full duplex £585 (a)The price of WS4000 and WS3000modems includes a COMMSTAR II ROMand BBC Data Cable.

WS2000 V21/V23 Manual Modem £92 (b)DATA Cable for WS series, PC or XT £10 (d)Auto Dial Card £27 (d)Auto Answer Card £27 (d)WS2000 SK I Kit £5 (d)

This offer can only apply if it is specified at thetime of placing your order for the modem.

RT256 3 PORT SWITCHOVERSERIAL INTERFACE3 input 1 output or 1 input -3 outputmanual channel selection Inputoutput baud rates. independentlyselectable 7 bit/13 bd. oddieven'nonepanty Hardware or softwarehandshake 256K butler. mainspowered 1375 (b)

PB BUFFERInternal butler for most Epsonprinters Easy to install Ins)suppliedPB128 128K 199(c)

UVERASERSuv1T Eraser with built.in timer and mains indicatorBuikin safety interlock to avoid accidental exposureto the harmful UV raysIt can handle up to 5 eproms at a time with an averageerasing time of about 20 mins £59 + E2 p&p.UV1 as above but without the timer E47 + £2 p&p.For Industrial Users. we offer UV140 6 UV141 era-sers with handling capacity of 14 eproms UVI41 hasa built in timer Both otter full built in safety featuresUV140 t69, UV141 p&p 12.50.

EXT SERIAL/PARALLELCONVERTERS

Mains powered convenersSerial to Parallel E48 (c)Parallel to Serial 148 (c)Bidirectional Convener 1105 (b)

Serial Test CableSerial Cable switchable al both endsallowing pin options to be re-routed orlinked at either end - making it possibleto produce almost any cableconfiguration on siteAvailable as M,M or MuF £24.75 (d)

Serial Mini Patch BoxAllows an easy method toreconfigure pin functionswithout rewiring the cableassay Jumpers can be usedand reused £22 (d)

Serial Mini TestMonitors RS232C and CCITTV24 Transmissions.indicating status with dualcolour LEDs on 7 mostsignificant lines. Connects inLine E22.50 (d)

CONNECTOR SYSTEMS

I.D. CONNECTORS(Speedbaock Type)

No of Header Recep Edgeways Plug 'acre Conn

1 110p 1159 1209200 145p 125p 195926 1759 1500 240934 2009 160p 320p40 2209 1909 340p50 235p 200p 390p

SOFTY IIThis low cost inlell gent eprom programmer can program 2716 25162532 2732 and with an adaptor 2564 and 2764 Displays 512 bytepage on TV - has a serial and parallel I/O routines Can be used as an emulator cassette lilted aceSoftyii 1195.00(b)Adaptor for 27642564 C25.00

SPECIAL OFFER264-25 £3.20 (d);

27128-25 £3.50(d)27256 £5.50 (d);27512 £9.00 (d);

6264 LP -15 £2.80 (d).

D CONNECTORSNo of Ways

9 15 25 37MALE:Ang Pins 120 180 230 350Solder 60 85 125 170IDC 175 275 325 -FEMALE:St Pm 100 140 210 380Ang Pins 160 210 275 440Solder 90 130 195 290IDC t95 325 375 -St Hood 90 95 100 120Screw . 130 150 175 -Lock

EDGE

CONNECTORS2 6 -wan (commodore)2 10 -way2 x 12 way Ivor 2012x 18 way2 x 23 way 1288112x 25 way2 x 28 way iSpectiumt2x 36 wayI x 43 way2x 22 way2 x 43 way

x 77 way2 x 50 wayiSI00conn-

0 1 O156- 3150p

00p

- 3409509- 1

1759 220p2259 220p2009 -2509 -2809 -90939594009 50096009

AMPHENOLCONNECTORS

36 way plug Centronics(solder 500p CC) 475p36 way ski Centronics(solder) 550p (IDC l 500p24 way plug IEEE (solder)475p ( IDC 475p24 way ski IEEE solder)500p (IDC: 500pPCB Mtg Skt Ang Pin24 way 700p 36 way 750p

RIBBON CABLE,grey nwfrel

10 -way 40p 34 -way 160p16 -way 60p 40 -war 100p20 -war asp 50 -way 200p26 -way 1209 64-wai 2909

TEXTOOL ZIFSOCKETS 24 pin 67.6028.pin re 10 40 pin C12.10

EURO CONNECTORSDIN 41612 Plug Skt2 X 32 way St Pin 230p 275p2 x 32 way Ang Pin 275p 320p3 x 32 way St Pin 260p 300p3 x 32 way Anp Pin 375p 400pIDCSkIA+B 400pIDC Skt A + C 400p

For 2 x 32 way please specifyspacing (A + B. A + C;.

GENDER CHANGERS25 way D type

Male to MaleMale to FemaleFemale to Female

£10£10£10

14 pin16 pin18 pin20 pin24 pin28 pin40 pin

DIL HEADERSSolder IDC

40p 100p50p60p

1109

75p100p 150- p

160p 200p200p 225p

RS 232 JUMPERS125 way Di

24 Jingle end Male24 Single end Female24 Female Female24 Male Male24 Male Female

0500£5.25

01000C95009 50

MISC CONNS21 pin Scart Connector 200p8 pin Video Connector 200p

DIL SWITCHES4 -way 90p 6 -way 105p8 -way 120p 10 -way 150p

ATTENTIONAll prices in this double pageadvertisment are subject to

change without notice.ALL PRICES EXCLUDE VAT

Please add carriage 50punless indicated as follows:(a) £8 (b) 12.50 (c) 11.50 (d)

11.00

TECHNOLINE VIEWDATA SYSTEM. TEL: 01-450 9764 Using Prestel' type protocols. For informationand orders - 24 hour service, 7 days a week


11(1:01 NO

89 11:41N3

co1-zLu

0CI

Lt

Lu

0U

2 8844

! !8282

nV8

8;A28a22$82882;c1q2t2rr.$5010Pc.S$4B5cS8scSr2:1

, ,,,

212! giM2PlieiglINMglgggn.W§§i6

--

I--

An

*vv..

R85t9282222220,e2,13 88882888888 888

ss

74;PWW

IN !M

UM

::88888 22222

2 %i

00000 !Aomas

21g

tWWi 2H222

NNNNANN

4282 48

11.6,44

re:

RBa

RA.1

.mN

ryP.%

88

4

8888

LT

I

88

Ed

8888888888228

ly.'888--g',1,g,MILTJVYV

8 88mm

88

8284282828888882888282S888888888822

osiciiSneienniolciplA nN.wn n

zzn:uir.invmeeinnkeir

<0

2ggeg

!al in8i§881 Main

881.4

28

888888888

RRR:474.4:1;k

Esa.6-00L

'2

III828888888 282222242A82282,t2882888222228822428

g. -,g

3..8,le.,AA . ....e4.

ilii1a50; 548e28"iliSIONOW39V727Pf2NIA

4tiTilrgi MESIVANWYVYMMWE

3aw

urMS

Ma

§§

!!yR4.1

S 288.4 8 8

nni 4 4

4

g3

28222.48482r

888282228 22:528222288M 888"g222

_n annr.mnMuli.-nrvOW,WMPi NN.-barC4t.

42288 8 888 2288

.. .A.s

gee 88888888888 888

"WW.0 W

.WMB155

E ag EEEE

Rall"S8$SSS.148R

S28RSSSSS$8SSS$SISSSW

;SRSR

R$rrr.r2228r82282vm

mr5pm

smsgO

A

1:111iitF,338-g.gaggRR

RR

RR

AA

A.1A

§n',Y,A

!!,Milvii!!!!;;;;V

;lcomizA

tt;:z1,4-4#,,f,ig,i,zg,g,,.i,

282824322882888288282284282888 W22888R

88!!8811822!F!!!!!!M!!!!9

FF

TE

0-,,,con,,,,,!n!

i.!

Iet%,

-A AA2gan

NA06zL.Z.-....,

gAqtaigRqralWg:8,W,,-,,IIIAAF,?82=4,74,1*122R2,22.-

R8 N

14_-

22261"2222;;;2239333322iiiiinYailtli'll/MTMTT#W/YoaHm03:t mA33

8s8$5888.le882E88.T.8888A888e214888888288888e8888E8282.8888Vr8388M8828588.8282.8$8

,4rinci.On^On..,n4n.."4^rinn.,444e4444nAnnood.-.4 , cia ,

MildiCrIbactiMunnirviqq8anirAhL7,;,,,_§,..51'14.nPc.41g1FrAn4,T5a,

zi,g.,AAA88888 8888 ,,mnomn.P;12-30,wiRA,T,,A,ArM2R-7,2,4,F474,,; 22A2

xr4,4;agOw,i;i46666666666566636656665A.A.Agiu

oU0Out.L.wwwwum222222222222222222M22m222232

aa

888888888ggR8RMR

nrinnw..nnivoci

0ElEj000

,Wa>"8'iZ2ZZmExt741P;

[1.0.0.0Z444440W

MM=10.22222200

V122 88

,14

gIDT i'

-zJ-xxtoohic

8222RR288821rg

,,,,

SAIA4RSgsprzsmss32$112SS5MgMRS2MR2s8C3220:8P8IPMSTVRV813S2S83RSS8S88,1M72gg8RMR2gg2ggs888851sw.22

0. ,,,,, .-..o.n....44no4400.-^^ono46.-4000.-oomed0000.-noorn.-0004.-nnn ,, 44noiWn:o.-oo--.-n-.-oononnn

000

meatligE

ramm

m:=

N§E

inm,A

nmainm

inRw

ilmftrail!!!E

!!!4==

ifiiiii:,?...2gPS,T8288888A88888888242828288gA$$$

8gs9!RA:412musgs48s8,7,22;27-Pgag5IEUEMEEE

,IM4Y3.YYYY,Y.YYYYYYYYYYYY,Y.YMy0,

XP82282288822828RR32288 8RPAe888228822288288828844R8828882888288288882

..

.^n^nn7OO:c4rinn..2

r2,T222A;28F,AAppRUAiRPIAPlefZig8218AW4-49;_,TAR88;;:340fin,NigilF

===n1M2anorAtramwomom222222wiginirOa IAAMA2AAANNOA00A MM

882288282222282'4,9888RR8822288288888R228888RR88888288RR8R888'

RA

an

W§MBiaLig=

NN.....NNNNNNNNN

,,NNNNNNNNN,,,,,,,, NNNN ,,,

NNNN NN

NN ,,,

,n=!!!!2!!!!WWWW,

fggls!!!2!!283228

EEEF.EnEUMEM

nnnnnnnnnnnnnnnnn

111

XX

ZX

XX

XX

ZZ

ASZ

XX

X2R

XZ

ZZ

82!87.1.7.88282RPA

SIA3M

8000"v2282222286!!!!!2282AN

NN

N:288!8M

!CC

SAA

222228882 ,,,,,!E!RE!

§mAggEL-,c9:iF,r4-,,ilimi§r,F,Hratic,-,H,Nazziataaar,!=g2T.TT2=1,1=CMINEN:tf,12,!!!:,;1

,--ugm

P.2222g2

288882

.Ct82,

2228828222228

nrinn4OOndO

22ZZ

Ig27,

2828882

*4'11

5188

aam

88888,822

gAi

zz 9

83

222

cEE

#

88888 228822.2428 288822

L1-1,;

2.9-2

3:44

1:5,5

Li

uas

,,"

eg1.4:1.

R711248:27.482,9882822P827.822484848R89828822822888228222R2284XXAM7.

0000000000000000000000000000. -..-.-non , .-00000-00000000000000n000000.

No.o-,m

eownw

,0-,m4u14,m

oo-,nyoP.

N NNNNNNNNNNNN NNNNNP.NNNNNN2woo

NNNP.P.NNNNNNNNNNNNNNNNNNNNNNNNNNNNN,,,,,NNNNNNNNNNNN N

N ,

NNN

000000

!&:'T:Tp7::::!:!!!:71,!n!!!!!!!!!!TMP2,TIP*POPO!!!!!!!:::::ff4,7PTNN!::::::!!!!Prf!!!!!!"'7'""""2"11"g2"*""

NN n n n n NN

' 0983 292847 Xen-Electronics24 hour Answering Service

Specialised Electronic Component SuppliesJust a small selection from 100's of thousands of stock items

4000 SERBS

4011UB

0160160.16

7413 SERFS74LS0074LSO474LSI3

0 20020028

4012B 0.21 74LSI4 0 4240138 030 74 LS20 0 2040178 028 74LS32 0204019B 050 74LS37 0 2040208 0 66 74LS42 04240238 025 74LS85 0 624024B 040 74LS123 06740258 0 20 74LS132 05440288 0 26 74LS139 04640308 029 74LS193 09840408 0 50 74LS240 06740428 041 74LS244 0.5840508 0 29 74LS245 0.7540538 050 74LS365 04240638 0.70 74LS373 0 5840668 0 20 141K SUMS40688 0 21 74HC00 0.3340698 am 74HCO2 03340708 0 20 74HC04 0.33407IB 0 20 74HC11 0.33407813 021 74HC85 0834081B 016 74HC139 058451013 046 74HC200 10145118 046 74 HC240 0.584514B 0.91 74HC244 09545188 040 74HC245 0924543B 058 74HC251 0 4345478 1 23 74 HC273 0 8340174B 048 74HC354 0.51401928 056 74HC373 079401938 056 74 HC374 079401948 0 65 74HC4002 0.714019513 083 74HC4022 0.54403738 1 10 74HC4040 0.54403748 I 10 74HC4060 0.56

THIS MONTHSES% DISCOUNT

BEFORE

SPECIAL OMRIF ORDERED

Dm July

4001UB ICM72 71P1 MTP8N104011UB 11.074 N SG3526N4011B BC182 7810540178 BC2I2 J11240288 BC5468 2N264640668 BD233 BAT85451813 BSR50 GM472W

T2 0983 29284724 hour Answering Service

MICRO I LSI DIODES MIER DIODES UPI,* 163MC0.140AP 390 N40. 0.04 1326 005 2N2646 0.55MC68488P 804 N4190 002 BZY80C44, 006 2N3055 050280A -CPU 180 N4933 025 BZY88C5V1 0.06 2N3704 010280A -DART 428 N3891 1.89 BZY88C7V5 006 2N3819 0.4028011-PI0 168 N5339B 0.36 8ZY88C9V I 006 2N5307 020280A -S10/0 496 N5401 0.12 BZY88C I 0 0.06 2N5308 020UPD41256-15 265 31DQ03 0.64 BZY88C11 006 K SOCKETSTC5516APL-2 300 BAT85 0.10 BZY88C15 006 TURNED PMICM72 I 7IP1 421 BYV32-100 124 MUDGE RICS 640WAYAD I DA CONVERTIRS BYV95B 0.18 KBPC808 142 Price 'PIN 200AD7525LN 19 25 BYV95C 0.20 SK8202L5A 043 NAM LOW COSTDAC8ON-C81-V 19 50 BYX71-600 1 12

WOOSM31.140

095 6.40 WAY"ADC1210HCD 45.55 8Y206026 Price 'PIN"ADC1211HCD 3996 40H120 116 TRANSISTORS K SOCKET

40HF R20 116 BC107 009 ROUNDM16-100 093 BC108 0.08 3 PIN 017M16-10OR 093 BC182 0.08 8 PIN 038M25.100 127 BC212 009 10 PIN 042M2510OR 127 E1C3278 008 SIL SOCKETI.R. OPTO BC5468 0.09 STMITPS7034 125 BC556A 0.08 6 WAY 012TLN1054 044 BD131 0.40 12 WAY 022TLN105 04C BD233 0.33 20 WAY 056

BF259 0.26 CAPACITORSBSR50 0.44 A = AXIALBUS48P 265 4 74F635 -A 008BUS98 570 10u.135V 005141520 175 220100V 0 171112 030 33p116V 0051RF840 759 471...F35V 0.10MTP8N10 I 85 100p.F25V 0.07MI3001 1.46 1004F50V 017MJ2501 152 330016V 0.12TIP110 0 36 4704110V -A 0.30TIPI 15 039 474550V amTIPI21 039 1000µF10V 0.15TIP126 039 2200µF16V 0.30TIP141 I Sr1 4700µF25V 158

DAC0800LCN 2.45"DAC1200HCD 18 84"DAC120IHCD 15 15ICL7109CPL 840AD7542KN 18 94M RMI011 ICSSL4860P 220SL490DP 1 92ML926DP 2.73ML928DP 2 73OR)) Precrsion Op amp 1 43

UGN3010 Hal ENect IC 2 58074 Quad OprArop 00000 661436 High Volt Op Amp 5701458 Dual Op'Arnp 041311 Comparator 044324 Quad Op Amp 0413340 Dec Alienator 130398 Sangre 6 Hold 395714 Precr5on Op Amp 448741 Op Amp 0187555 555 Timer 020759 Power Op Amp 2723514 PSU Controller 2853516 PSu Controller 36935161 righ Temp Above 49:7660 Neg Volt Gen 1 7E

Voltage RegulatorsIA fixed voltage

Plastic 10220 Pack7800 7900 Series

245 to 245 0 450.1A fixed voltage

78100 79100series Plastic1092 Pack

155 to 155 0 27

0.02

CAPACITORSSCREW TUMOUR150µ1450V 6.32470µF 250V 570470µ1385V 9.424700µF63V 627-5500040V 525100000.40V 312DISC CERAMIC47pF63F 003120pF63V 0.05100pF5OV 0.031000pF63V 0022200pF63V 0.034700pF63V 0040.047µF5OV 0040 1 p.F25V 0.050 1µF63V 014mosiounecNUNN:AYER50/100V5/10/20%100p1 0 1µ1 011

POLYESTERALL 250V0 01 0 4741 0 08POLYSTMENEALL 160V47pF2700p1 0 10TANTALUM10µ16V 0096.8µF1OV 0.12touriov 0.1010µF I 6V 0.1322p.F16V 3.21331./F16V 0.3247µ.6.3V 0 23100p.16.38 057150µF6 3V 094

RESISTORSCARBON FILM025W 5%1R - IOM 1.5p0.5W 5%104 - IOM 2 5pWM FILM0.4W 1%

1M 35pENAMELWIRE WOUND25W51k_ 1h., 216W 5%1R2 - 2K4 0.46CERAMIC17W 10°.1F- i 020Sit NETWORKS0.125W 5%MOM (9PIN)

10:)K 031IMERNISTORWA (ILK)4K7 GM472W I 95POTEIMOSIMIRSCOUffivir SOPCB TOP ADJUST1004 - 200K 030PCB SIDE ADJUST5004 - 200K 0.30EAULITTURN 341-10PCB TOP ADJUST100R - 2006 0.85PO SIDE WAIST200R - 200K 085MASTIC TRACK-SIIINCOSRE56 18 25

* * * PROJECTS * * *Distance Measuring InstrumentAn di I Ovate temperature r. or,,pensatedUltrasonic measuring device. Basicallydesigned for measuring between two parallelobjects up to 26ft (656 with OptionalParabolic Reflector)Applications: Room Dirnentioning, CarReversing Surveying, Robotics. Intrusion.height gauge, and lots moreOUTPUT: Four Digit BCD (Multiplexed).Interlaces indirectly to a four -digit LCD displayboard (optional)Kit comprising of: PCB. Components.Transducer. Slide switch. Push switch.Thermistor. PP3 Battery connectorKIT PRICE 22.95BUILT AND TESTED 34.95Optional ExtrasLCD Display Board comprising:4 -Digit Liquid Crystal Display with Drivers andon board DF Oscillator.KIT PRICE 13.95BUILT & TESTED 17.95Ultrasonic Parabolic reflector distances upto 656 have been achievedPRICE 2.95

"SIN Parallel CaMmelcs CsavoMerIdeally suited for computers that can notsupport Parallel PrintersKit comprising: PCB. Components 36wayCentronics IDC Plug and Patch LeadKIT PRICE 17.95BUILT & TESTED 25.95Sinclair QL 'SERI or 2. Plug 1.4225W D' Type Plug or Socket 0.60Car ICE Warning IndicatorKIT PRICE 5.95BUILT 8 TESTED 8.95

LE.D.'S 4.9 mm DIARED TLRI 13A 010GRN TLG113A 0.13YEL TLYI134 017ORGTL0113A 021LID'S E.ImmRED T1.4123 008GRN TLG123A 0.11YEL TLY123 0 13ORGTL0123 017

LLD. INPUTS0.3CA TLR332AN TLR3330.43'CA TL4342AN TLR3430.50CA TLR358AN TLR359

0 890 89

089089

0.89089

D TYPE COMECTORSSOLDER MONT

9 WAY SK9 WAY PLL.9 WAY SHELL15 WAY SKT15 WAY PLG15 WAY SHELL25 WAY SKT25 WAY PLG25 WAY SHELL

0.430.380.980600531.070600531 16

PLEASE ADD S1 PAP and 15 . VAT Datasheets zero rated D to sheets 50p sae treeon request earl component Stock itemsnormally by return of post Please ask us toquote for items not listed Pan numbers areexact or nee. equivalents Prices correct attime of going to pressCoil winding lac Atv available

NAvarlable until stocks are exhausted"EPROM Programming avartable 0 Olp per8 bit byte mm chg 15 00 £2 SO for dnpiicahone

**ISO Bond Catholic/ BoardIhis simple to understand L80 CPUbased board has all the necessary hard-ware to control menial to most complextasks Hardware includes 16 output linesand 16 input lines. 2K static RAM and2K EPROMKit cornprisIng of -PCB. 180A CPU. RAMEPROM. LOGIC. 4Mhz XTAL. R's & Cs.CONN'sKIT PRICE 19.95BUILT 8. TESTED... ...... ............... ...29 95

XEN-ELECTRONICS. UNIT 4 SAMUEL WHITES EST. COWES. ISLE 0 F WIGHT P031 7LP

ENTER si ON REPLY CARD

Advertisements are expected to conform to rules and standards laiddown by the Advertising Standards Authority. Most do. The few that

don't we'd like you to write in about.And if you'd like a ,copy of these rules for press, poster and cinema

advertisements, please send for our booklet. It's free.

The Advertising Standards Authority.We're here to put it right.

ASA Ltd.. Dept. Y. Brook House. Torrington Place. London WC I E 7H N.

This space is donated in the interests of high standards of advertising


Leetronex 87The 24th Leeds Electronics Exhibition (Leetronex) takes place at

the Department of Electrical and Electronic Engineering,University of Leeds, between 30th June and 2nd of July. With over

100 exhibitors and a programme of lectures, the organizers areaiming to re-establish it as the best electronics show outside

London.

The exhibition was created in 1963through requests from a number ofelectronics instrument manufacturers

who wanted to demonstrate their equipmentto the expanding higher education market.The equipment was shown to a selectedaudience of university staff. The event was sosuccessful that it was repeated the followingyear and Leetronix became established. Itgrew to a peak of several thousands ofvisitors from all over the UK in 1979.

The economic recession of the early 1980sreduced the number of exhibitors and visi-tors. Last year, the Department of Electricaland Electronic Engineering took over therunning of the show and made a major effortto re-establish it as "the best electronics

exhibition outside London." The 1986 ex-hibition increased its attendance by nearly50% over the previous year. The presence ofover 100 exhibitors this year suggests thattheir efforts have been rewarded.

The re -introduction of a programme ofseminars, organized by the Yorkshirebranch of the IEE, also helped to restablishthe status of the show, already the longestrunning electronics exhibition in the UK.

The exhibition has several qualities thatdistinguish it from other shows; Any profit isused to improve the undergraduate teachingfacilities; last year's profits were used toenhance the computer teaching laboratory.The show is supported by a number ofleading national and international corn-

panies and offers a link between industry andhigher education.

PROGRAMME OF LECTURES

Lectutes, sponsored by the Department andthe Yorkshire Centre of the IEE, will takeplace in the Lecture Theatre (room 192) onthe first floor.Tuesday 30th June1100hThe changing technology of electronic com-ponents and assemblies.H.W. Ellis, Mullard Ltd.1400hCustomized design of integrated circuits.P. Forshaw, Ferranti MicroelectronicsCentre.Wednesday 1st July1100hDBS receiver architecture and technology.D.W. Walton. Thorn -EMI Ferguson Ltd.1400hSatellite tv - the present and the future.J. Hazell, British Telecom.Thursday 2nd July1100hModern tools for microprocessor softwaredevelopment.L.M. O'Carroll, Computer engineeringgroup, DE& E E. University of Leeds.

5,

52

50 L 49 48

54 55

R- 21 777 22,

7 219 7,9230 Fj

2..760 .7,1151

71JL17 .0,

7

2 25

5 I 4

12

- 0(.7)

cc

311

1: 141 1

SEMINARLECTURETHEATRE

1

ELECTRONICS& WIRELESS WORLD AID

FIRST

ORGANiSFDm( t

WIUR S

BAR

L'3, 1 'I 1 143 1

1201 1 1

119 117114

ttgIts

135 j

4-F.-108 107 106 105 104 103

101


4Mbit chip uses`trench cell'

The first laboratory samples havebeen produced for a dynamicram chip that can store fourmillion bits of data. Produced bySiemens in collaboration withPhilips, the 4Mbit d -ram uses a'trench cell' in which a trenchonly one micron wide is etchedfour microns deep into the sili-con. Each trench cell, with acapacitance of 40fF, stores onebinary digit and occupies an areaof only 5p.m2.

To obtain the more than 4million memory cells on a siliconchip, 450 process steps in c-mostechnology are necessary. Com-pared with the 1Mbit d -ram(54mm2), the storage capacity ofthe 4Mbit device is quadrupledwithout doubling the chip area(91mm2). Typically the 4Mbitchip can store the equivalentcontent of about 250 pages oftypewritten text.

The Siemens part of the pro-ject has been supported by theGerman government to the tuneof DM240 million. Production isexpected in 1989.

Engineersregister

broadenedThe Engineering Council has setup a register for people who havegained either a degree, a HigherNational Certificate or a NationalCertificate in engineering as thefirst step towards becoming aqualified engineer.

Up to now the Council, whichhas 300,000 Chartered En-gineers, Technician Engineersand Engineering Technicians onits official register, has reg-istered engineers in those threecategories only after they havecompleted three stages: achievedthe exemplified academic stan-dard (known as Stage 1), com-pleted an approved trainingperiod (Stage 2), and gainedacceptable experience and pro-fessional responsibility (Stage 3).Now the Council's board forengineers' registration hasapproved the first list of candi-dates for registration at the Stage1 academic level.

Professor Jack Levy, the Coun-cil's director for the engineering

[UPDATEprofession, said: "We have thelargest professional register ofmembers in the United King-dom, but the country needsmany more to help us improvethe competitiveness of Britishindustry. We have already per-suaded the Government to pro-vide more engineering studentplaces in universities andpolytechnics but we are pressingfor even more."

He stresses the importance ofregistering as soon as possibleafter gaining a recognised de-gree, Higher National Certificateor National Certificate qualifica-tion so that they quickly proceedto becoming qualified engineersin one of the three categories.The Council and the professionalengineering institutions adviseand encourage young entrants.

"Our titles and designatoryletters of Chartered Engineer(CEng), Technician Engineer(TEng) and Engineering Techni-cian (Eng Tech) are recognisedguides to employers and othersof the competence and standardsachieved by registered en-gineers," says Prof. Levy. "Wenow urge the larger numberswho are completing their educa-tion in engineering and technol-ogy to register with us." En-gineering Council, 10 MaltraversStreet, London WC2R 3ER. Tel:01-240 7891.

Domesdayextensions

Development has been designedto extend the applications of theinteractive video system andDomesday discs developed by theBBC, Philips and Acorn Compu-ters.

A new videodisc provides theusers with a practical guide toecology, taking as its basis thesimulation of a Devon naturereserve. The 'Ecodisc' enablesusers to draft a plan for manage-ment of the reserve and its activi-ties by discovering, learning andapplying ecological knowledgeand concepts.

Floppy -disc software offers en-hanced facilities for the use ofthe Domesday discs. One enablesthe extraction of relevant pic-tures and information which canthen be displayed independently.In autumn a further softwarepackage will enable users to inte-grate their own information with

the maps included on the discs.Next year, an additional disc

for the Domesday system willcontain detailed maps down tostreet level with updated and newdata sets for specific sectors ofindustry and commerce.

Spray -on super-conductors

Scientists at IBM have found away to spray -paint large andcomplex surfaces with high-

temperature superconductormaterial. This raises the prospectof inexpensive, easy -to -applymagnetic shielding, computerwiring and other applicationsthat might benefit from its prop-erties and workability.

IBM has coated items of va-rious sizes using an industrialtechnique called plasmaspraying. Plasma spraying quick-ly heats a material to thousandsof degrees and instantly depositsthe substance on a surface whereit resolidifies. After coating, ob-jects are reheated to anneal thesurface. At this stage the coatingbecomes superconductive. Thematerial's superconductingproperties were discovered lastyear, and the researchers believethey are the first to quickly andeasily coat complex shapes suchas pre -formed wires, contouredand flat surfaces and even tubesmade from ceramic. quartz andmetals.

The materials, combinationsof yttrium, barium and copperoxides, resemble flat black paint.After annealing, they become su-perconducting in the tempera-ture range of liquid nitrogen -'warm' enough to be practical formany scientific and industrialuses. (Liquid nitrogen boils at77K.) Most materials and wiresthat IBM researchers have coatedbecome completely supercon-ducting at temperatures as highas between 60 and 82K. In addi-tion to their ability to pass cur-rent without resistance, super-conductors are impervious tomagnetic fields, and might serveas an easy -to -apply and econo-mical magnetic shielding. Su-perconducting wires for compu-ter chip packages might also bemade by plasma spraying. Coatedthin lines have been added toceramic substrates used for inte-grated circuits and microscopicholes have been successfullycoated.

EXHIBITIONS& CONFERENCES

22 - 26 June 1987Laser 87 Opto-electronics, mic-rowaves.8th International congress andexhibition. Munich Trade FairCentre, F.R. Germany, MMA,Messegelande, Postfach 12 10 09.0-8000 Munchen. FRG.23 - 25 June 1987KBS 87 & Software Tools 87.Knowledge -based systems andsoftware. Wembley ExhibitionCentre, London. Online Interna-tional, Tel: 01-868 4466.24 - 26 June 1987APRS Show, (professional soundrecording) Olympia. London.24 -27June 1987SMT 87 Berlin: Surface mounttechnologies, International Con-gress Centre, Berlin. Details fromAMK Berline, Postfach 19 17 40,Messedamm 22, D-1000, Berlin19, FRG.26-30 June 1987BKSTS 87. 10th internationalfilm and tv technology confer-ence and Exhibition, MetropoleHotel. Brighton, BKSTS. Tel: 01242 8400.30 June -2 JulyLeetronex '87 the 'premier ex-hibition of the North' Leeds Uni-versity. Tel: 0532 431751 ex 328.30 June -3JulyExhibition of electronic musicalinstruments and systems at theLondon College of Furniture,Commercial Road, London El.4 -16JulyElectronic Design AutomationShow, Wembley ExhibitionCentre.7July 1987World final of the Micromousecompetition, Maze -solving, selfpropelled computers will be run-ning round the IEE. Savoy Place,London El at 1730h. Furtherdetails, and rules and entryforms, from Andrew Wilson atthe Institution. Tel: 01 240 1871Ext. 260.28 August -6 SeptemberFunkausstellung; Internationalaudio and video fair Berlin (in-corporating MediaForum), Inter-national Congress Centre, Ber-lin. Details from AMK Berlin,Postfach 19 17 40, Messedamm22, D-1000, Berlin 19. FRG.15-18 September 1987Design Engineering Show, NEC,Birmingham, Cahners Exhibi-tions. Tel: 01 891 5051.EED 87. electronics in engineer-ing design, NEC, Birmingham,Cahners as above.Test and transducer; internation-al conference and exhibition.Wembley Conference Centre,London. Trident International.Tel: 0822 4671


X-rays can pre-ionize lasers

The use of X-rays to pre -ionizethe carbon dioxide gas of high-powered pulsed lasers is beinginvestigated at the British Aero-space Sowerby Research Centre.

Conventionally, gas preioni-zation is achieved by subjectingthe gas to ultra -violet radia-tion produced by spark dis-charges triggered off within thecavity of the laser. The researchcentre has produced the sameeffect by subjecting the gas toX-rays instead of ultra -violetradiation. Among the advantagesof this is that greater volumes ofgas can be ionized, enabling las-ers of much higher intensity tobe developed.

The area where the pre -ionization occurs can be deter-mined with greater precision,

[UPDATE

leading to more efficient ener-gizing of the laser. Laser tubescan be simplified, as only twoelectrodes are needed, and thelaser gas remains purer as u -vradiation can cause the gases todissociate.

Experimental CO2 laser with x-ray pre -ionization is claimed byBritish Aerospace's Sowerbyresearch laboratories todemonstrate greater laserefficiency and less gasdissociation.

EXHIBITIONS& CONFERENCES

23-27 September 1987PCW 87; 10th Personal Compu-ter World Show, Olympia,London.29 September -1 October 1987NAV 87. Navigation data, dis-semination and display confer-ence and exhibition, HeathrowPenta Hotel, Organized by theRoyal Institute of Navigation.Tel: 01-5895021.Semiconductor International:design, assembly, test, materialsand chemicals. NEC Birming-ham, Cahners Exhibition, Tel:01-8915051.5 -8 October 1987HDTV 87; International collo-quium, Ottawa, Canada. Detailsfrom HDTV colloquium. JournalTower North, 300 Slater Street,Ottawa, Ontario K1A OCB,Canada.

Technologicalachievement

A high proportion of this year'sQueen's Awards for Technologyhave gone to electronics com-panies.

Integrated switching. AB Auto-motive Products for theirprocessor -controlled switchingsystem for use in cars. The sys-tem for the Jaguar X.I40 has over200 auxiliary items that requireswitching.

ISO network system. BICC DataNetworks for the development ofthe Isolan system of hardwareand software links for a local -area network that conforms tothe ISO standards. The systemallows the mixing of coaxial andoptical fibre cables within onenetwork.

Computer -controlled looms.Bonas Machine Company forcomputer -aided patterning forJacquard fabric weaving looms.Designs can be programmed in afew hours compared with fourdays for the old punched -cardsystem.

Radio -controlled switching. TheBBC in collaboration with theElectricity Council for remoteswitching of lItctricity timeswitches. Low -frequency signalsare added to the BBC's long andmedium -wave broadcasts with-out affecting the audible signals.

Heat -detection system. RoyalSignals and Radar Establishmentin collaboration with EEV tubesfor the development of heat de-tecting video cameras. Thepyroelectric vidicon tube is cap-able of detecting temperaturedifferences as little as 10-3°C.

Night vision (twice). RSRE/EEVare also responsible for theaward -winning night -vision sys-tem for aircraft, using new imageintensifier tubes. Also The RoyalAircraft Establishment for theirnight vision system uses infra-red sensors, night -vision gogglesand head -up visual displays.

SMC autoplacement. DynapertPrecima for automatic place-ment of surface -mounted com-ponents. Machines can place upto 6000 components in an hourand can be programmed tohandle up to 120 different com-ponents types.

Oil reserve simulation. Explora-tion Consultants of Henley onThames for Eclipse computersimulations of gas and oil re-serves.

Surface -mounted p.c.bs. Fer-ranti Computer Systems formetal -core multilayer p.c.bs thatavoid the problems of thermalexpansion and heat dissipation.

Computer -controlled cam lathe.The Litton UK camshaft systemautomatically compensates forgrinding -wheel wear and

achieves much higher accuraciesthan previously possible.

CD mastering. Nimbus Recordsfor developing their own systemof mastering compact discs, in-volving coating the masters withphotoresist 0.12µm thick, en-coding of digital signals to con-trol the laser writing beam, con-struction and control of themastering lathe and control ofthe plating process. It cost abouta tenth of the alternative system,exceeds the capabilities of thatsystem and meets the expectedrequirements of the next genera-tion of CDs.

Colour radar. Racal Marine Datafor a digital scan converter incolour radar displays. It proces-ses derived from a conventionalradar scanner to be displayed in ahigh -resolution colour tv for-mat. The system combines high-speed computing, video proces-sing and memory managementinto a single small unit.

Self -calibrating data recorder.Racal Recorders for its Store-house tape recorder for data ac-quisition. Its automatic calibra-tion system allows the recordand replay circuits to be set up inless than ten minutes instead ofthe hours previously needed.

Optical -fibre lasers. STC De-fence Systems for 1300m lasersfor optical fibre communication.The devices allow repeaters to be30km apart at a data rate of

565Mbit/s, i.e. twice the rangeand four times the speed of for-mer devices. They are claimed tobe the sub-merged use.

Aircraft simulators. SingerLink -Miles Ltd for functionallydistributed simulation systemfor aircraft training. Processorsare linked to provide real-timecomputing power beyond thescope of super -mini computers.the system is used in the firstsimulator for the new Boeing747-400.

Network manager. Tech-NelData Products Ltd. of Banbury.the NMX Network ManagementEngine which integrates hard-ware and software systems know-ledge for fault detection, restor-ing, and diagnostics in a singleprocessor -based fault -tolerantdata communications.

Magnets for spectrometersVG Analytical Ltd. for the de-velopment of laminated magnetsfor fast -scanning mass spectro-meters. Existing magnets offeredlimitations in meeting the de-mands of capillary column gaschromatography. The companydeveloped lamination andmachining techniques to pro-duce magnets assembled from100 or more 0.3mm thicklaminations. They meet the newrequirements of medical and en-vironmental biochemical analy-sis equipment.


APPOINTMENTS

(

Advertisementsaccepted up to 12noon June 26 for

August issue

DISPLAYED APPOINTMENTS VACANT: £23 per single col. centimetre i min. 3cm ).LINE advertisements (run on): £5 per line, minimum £40 (prepayable).BOX NUMBERS: El I extra. ( Replies should be addressed to the Box Number in theadvertisement, c a Quadrant House. The Quadrant, Sutton. Surrey SM2 5AS).PHONE: SUSAN PLATTS, 01-661 3033 (DIRECT LINE)

( 'heques and Postal Orders payable to REED RI TSINESS PITLISHING rind crossed.

Fl £i31

rd

4.1

13

D

rs,

qq

Al

Irr F-7_ 1 e7 Hilda E Eat> Eg

RADIO DEVELOPMENTMANAGER

Hefts/N. London £17K neg + car

Britain's premier motoring organisation providesa broad range of services to its 2.5m members.and is committed to new technology in achieving

growth and higher standards.A senior telecommunications engineer with a background inVHF or UHF radio systems. ideally involving data transmissionand aerial site selection. is now required for the new post ofRadio Development Manager. Having technical responsibilityfor the RAC's Computer Aided Rescue Service (CARS) project,the successful candidate will be a key part of the teamintroducing change and technical innovation. Age indicator26-45.Salary neg c.£17K + car, non-contributory pension, life andmedical insurance. Assistance with relocation wherenecessary.For further information and application form please telephone(0753) 867175 (24 hrs) or write to Alex Villiers, 3i ConsultantsLimited, 8 High Street. Windsor. Berks SL4 1LID. quotingref AV/674.

3i Consultants LtdI ILIM,11.1 Res( )(LILL', OR l',11)11

FA r 4D1:214> YfiX 16: *1 Btfl

Sinclair House, 74 WilloughbyLane, London N17 OSF

APPOINTMENTS Telephone 01-808 3050

THE UK's No. 1 ELECTRONICS AGENCYELECTRONICS ENGINEERS if you are looking for a

job in DESIGN, FIELD SERVICE, TECHNICAL SALESor SOFTWARE ENGINEERING.

Telephone NOW for one of our FREE Jobs lists orsend a full cv to the address below.

Vacancies throughout the UK to £18000 pa.

Co mmmm NE imCapital Appointments Ltd., FREEPOST London N17 OBR.

Please send me your list for Engineei

Name

Address

Post Code

0 01-808 3050 - 24 HOURS

Professional Career OpportunitiesThe Easy Way to look for your new job from thecomfort of your own armchair. Our well qualifiedconsultants will carefully match yourrequirements againstappropriate vacancies. cAmE

We have many clients seeking. Engineers and Technicians at all levels and we areArtirularly interested in hearing from you if you have experience in the following:

Technical Sales Quality Assurance ATE Design Technical Authors Test Engineering Maths ModellingYour next step is to complete and return the attached coupon ortelephone SIMON CANHAM on 0442 47311 or one of our duty consultants on

0442 212650 during evenings or weekends.

1111\ 1'i'( III(THE INTERNATIONAL SPECIALISTS IN RECRUITMENT FOR THE ELECTRONICS. COMPUTING AND OFFENCE INDUSTRIES/

Nlavl,inds Avenue. I leniel I It.iiip,tedd .11e11,, .111'2 41.1

t 1110._

I 6

(Mr/Miss/Mrs)

ADDRESS

POST CODE

TEL NO:

Type of position sought

Willing to relocate? Yes/No

Preferred locations

I Salary at presentKJ/SC

ref: WW

III ELECTRONICS & WIRELESS WORLD

CLIVEDENPROCESSOR BASEDWEIGHING EQUIPMENTTest 8 repair of food weighing systems£8,000 HampshireCELLULAR TELEPHONE SYSTEMSExperience of fault-finding analogueand digital systems. Training offered onA T.E£12,000 SurreyTELEPHONE EXCHANGESService and maintain PABX systemsthroughout so.rthern England.to £10.000 - car BerkshireTRAFFIC AUTOMATIONFault find and repair of digital controlsystems throughout the U.K.00.060 car MiddlesexCOMPUTER PERIPHERALSRepair a wide range of disc and tapedrives£8,000 BerkshireDOCUMENT READER SYSTEMSExperience in the repair of digital andmicroprocessor equipment both in theU.K and overseas.£12,000 Hampshire

Hundreds of other Electronic andComputer vacancies to £15.000.

Phone or write:Roger Howard C.Eng. M.I.E.E. M.I.E.R.E.

CLIVEDEN RECRUITMENT92 Broadway. Bracknell.

Berkshire RG12 1ARTel: 0344 489489

THE HATFIELD POLYTECHNICSCHOOL OF NATURALSCIENCES. Senior Technician -Electronics. Salary £7,536-£9,441. To beresponsible for a small ElectronicsWorkshop. The successful candidate mustbe an experienced electronics techniciancapable of fault-finding down tocomponent level and with a generalknowledge of scientific equipment. Startingsalary dependent upon qualifications andexperience. Closing date: 15 July 1987.Application forms and further details fromthe Staffing Office, The HatfieldPolytechnic, PO Box 109, Hatfield, Herts.ALIO 9Ab. or telephone Hatfield (07072)79802. Please quote reference: 291. 464

Project Engineering:The Mercury Challenge

Mercury

In under five yearsMercury Communications,part of the world-wideCable and Wireless groupof companies, hasprogressed from originalconcept to a position where

it offers a viable alternative telecommunications service. But it does notend there. Today we are still committed to continued growth involvingfurther, major, investment in facilities.

With our total commitment to digital technology, high capacity opticalfibre cable and microwave links we can offer the kind of professionalchallenge you will find hard to equal today.

PROJECT ENGINEERSOur London based team now has a few vacancies for Engineers tomeet the challenge of our technology and fully utilise their skills.Reporting to a Senior Project Engineer your role will include workingwith the Design Function both on design work and equipment details,dealing with suppliers in conjunction with other departments onprocurement matters and producing progress and status reports.

RADIO SYSTEM COMMISSIONING ENGINEEROur London team has vacancies for Field Based Engineers.

Your main role will be the commissioning of complex digital radiosystems and testing of alarms on a SCADA network throughout the UK.Extensive travel will be necessary.

Experience - five years' telecommunications experience, a recognisedtechnical qualification and knowledge of digital systems, ideally withhands on experience of microwave power and radio systems. Goodcommunication skills, commercial awareness and time spent in a projectenvironment would be useful. Current driving licence is essential.

In addition to an attractive negotiable salary there is an excellentbenefits package and outstanding prospectsPlease send a full CV to Susan Tomlinson,Mercury Communications Limited, St. Martin's House,140 Tottenham Court Road, London \X/1P 9LN,or for any furher information call on 01-387 9191, ext. 309.

Hardware/Software/SystemsL9,000- £25,000

As a leading recruitment consultancy we hove a wide selection of opportunitiesfor high calibre Design, Development, Systems ond supporting staff throughout the UK.

II you hove experience ,n any of the following then you should be talking to usforyour next career move.

ARTIFICIAL INTELLIGENCE * IMAGE PROCESSING * ANALOGUE DESIGNMICRO HARDWARE & SOFTWARE GUIDED WEAPONS C PASCAL

ADA * RF & MICROWAVE ELECTRO-OPTICS SIMULATION C'lREAL TIME PROGRAMMING SYSTEMS ENGINEERING ACOUSTICSSONAR RADAR SATELLITES AVIONICS CONTROL ANTENNA

VLSI DESIGN

Opportunities exist with National, International and Consultancy companies offeringexcellent salaries and career advancement.

To be considered for these and other reguiremeni. contact John S;Stephen Mor ev or forward a detailed CV in complete confidence auot, IRef. WW /66.

A STS Recruitment, 85 High Street, Winchester,Hants 5023 9AP. Tel: (0962) 69478(24 hrs).

Recnitment

ELECTRONICS WORKSHOPTECHNICIAN (Grade 5) required in theUniversity of Reading, Department ofPsychology. From mid -September 1987.The successful applicant will be required toadvise staff and students on electronicsproblems and to design and construct awide range of specialised equipment. TheDepartmental research and teachingactivities depend heavily on the use of

computers. The ideal candidate will havehad a recognised apprentice and at least 2years of varied experienced in electronics.Knowledge of BBC BASIC and of 6502would be an advantage. Salary scale £7696to £9086b p.a. Application form availablefrom the Personnel Officer, University ofReading, Whiteknights, PO Box 217.Reading, RG6 2AH, telephone (0734)875123 ext. 220. Please quote Ref. T.30A.

466

TO MANUFACi URERS. WHOLESALERSBULK BUYERS. ETC.

LARGE QUANTITIES OF RADIO. TV ANDELECTRONIC COMPONENTS FOR DISPOSAL

SEMICONDUCTORS, all types. INTEGRATED CIRCUITS, TRANSISTORS.DIODES, RECTIFIERS, THYRISTORS, etc. RESISTORS, C/F, M/F, W/W, etc.

CAPACITORS, SILVER MICA, POLYSTYRENE, C280, C296, DISCCERAMICS, PLATE CERAMICS, etc.

ELECTROLYTIC CONDENSERS, SPEAKERS, CONNECTING WIRE, CABLES,SCREENED WIRE. SCREWS, NUTS, CHOKES, TRANSFORMERS, etc.

ALL AT KNOCKOUT PRICES - Come and pay us a visit ALADDIN'S CAVE

TELEPHONE: 445 0749/445 2713HENSON LTD.

21 Lodge Lane, North Finchley. London, N.1215 rulnotes from Tally Ho Corner) 11613

INVERTERSDC -AC High PowerGardners sq. wave type GR75108PP: 50V DC 85AO/P: 240V 50Hz 4kVA £300Also 2kVA £200 - 1kVA £150

H8D Sinewave 600WI/P: 24V DCO/P: 230V 50Hz 600VA £240

CVTs: Cetronic Reguvolt 6kVA £290.5kVA £250: 4kVA £220; 2kVA £160.

GREEN WELD ELECTRONICS LTD443 Millbrook Road, Southampton

SO1 OXH. Tel: (0703) 772501/7837L0

BOX NosBox number replies

should be addressed to:

Box No.c/o Electronics &Wireless World

Quadrant House,The Quadrant,

Sutton,Surrey SM2 5AS


APPOINTMENTS

BEMUniversity of Wales

MSc in Electronic EngineeringAnalogue and Digital Systems; Computer

Engineering; Signal Processing;Communication Systems; Information

Engineering; Control and Instrumentation;Medical Electronics; Integrated Circuits;

Power Systems.

Diploma in Electronic Engineering(successful completion allowing entry to

the MSc scheme)

Circuit Design; Signal and DataProcessing; Digital Systems;

Communication and Radar Systems;Microprocessors and Computer Controlled

Systems.

Applications are invited for places on theabove full-time, one-year courses

commencing in October 1987.Further details and application forms may

be obtained from:The Assistant Registrar, UWIST,

PO Box 68, Cardiff CFI 3XA 4S8

INTELLIGENT SELF -MOTIVATING PERSON WANTED inlarge successful CD shop in central London for service andsales of CD players and audio equipment. Relevant City andGuilds, TEC or ONC qualification will be taken into consider-ation. Practical experience in digital equipment would be anadvantage.Please phone in first instance to Mr Hosein or Mr Bullat Covent Garden Records on 01-379 7635/7427

ARTICLES WANTED

WANTEDTest equipment, receivers,valves, transmitters, com-ponents, cable andelectronic scrap and quan-tity. Prompt service andcash. Member of A.R.R.A.

M & B RADIO86 Bishopsgate Street

Leeds LS1 4BB0532 435649

WANTED

STEWART OF READING110 WYKEHAM ROAD.

READING RG61PL.TEL: 0734 68041

TOP PRICES PAID FOR ALLTYPES OF SURPLUS TESTEQUIPMENT, COMPUTER

EQUIPMENT, COMPONENTSetc. ANY QUANTITY

AUCTIONS

On Friday 10th July at 12:00 noonJOHN RUSSELL 8 CO will hold an

important

SALE BY AUCTIONof electronic testing & recording

equipment 8. Computerdevelopment systems at: 3 Park

Road. Teddington Middlesex,

Spectrum analysers. signalanalysers & generators Comms.cable 8. mains test equipment,oscilloscopes 8. accessories,recorders, etc. etc. Tektronix,Hewlett Packard. W 8 G, etc.

View on site 10-4 Weds 8th 8 Thurs9th

' 01-640 4424 for catalogues.Auctioneers:

John Russell 8 Co.221 Western Road. London SW19.

FOR CLASSIFIEDADVERTISEMENTS

RING

SUSAN PLAITS

661 3033

TRAINEERADIOOFFICERS

e you looking for a secure snore -based lob whicn offersrewording career in the forefront of modern Tele-

communications technology... then consider

laming GCHQ os o Trainee Radio OfficerTraining involves o 32 week residential

course, !plus 6 weeks extra if you cannottouch type) after which you will be

appointed RADIO OFFICER and undertakeo variety of specialist duties covering the whole

- - .

We offer you: Job Security GoodCareer Prospects Opportunitiesfor Overseas Service AttractiveSalaries.., and much more.

To be eligible yc... Dr hope

to obtain on MRGC or HNC in aTelecommunications subject with

on ability to read morse of 20wpm.

Anyone with PMG, MPT or 2 years relevant radio operating experience is also eligible.

The Civil Service is an equal opportunities employer.

Salaries: Storting pay for trainees is age pointed to 21 years. For those aged 21Or over entry will be of £6,572. After training an RO will start of £9,758 nsing by 5

onnuol increments to £14,387 inclusive of shift and weekend working allowance.Write or telephone for on application

form to: -Was

laCHQ THE RECR(ITMFAT OFIICE, GCHQ, ROOM Ar 11014OAKLEY. PRR116 ROM), CHELTENHAM. G IA IS GL12 SAJ

OR TELEPHONE 10242132912/3

FIGOLLEDGE1

IELECTRONICSP

QUARTZ CRYSTALSOSCILLATORS AND FILTERS ofall types. Large stocks of standarditems. Specials supplied to order.Personal and export orders welcomed -SAE for lists please. OEM support thru:design advice, prototype quantities,production schedules. GolledgeElectronics, Merriott, Somerset YA165NS Tel: 046073718. 124721

SERVICES

BRIDGES waveformn/transistoranalysers. Calibrators, Standards.Millivoltmeters. Dynamometers. KWmeters, Oscilloscopes. Recorders.Signal generators - sweep, lowdistortion, true RMS, audio, RM,deviation. Tel: 040 376236. (26161

3 Si " FLOPPY DRIVESMITSUBISHI top quality new 3millisecond 80 track, only 32mm high,standard interface, will directly interfacewith PC's and will give 720K per disc. Veryquiet. Guaranteed in makers packingunopened. These are the best quality drivesavailable. £80 with full specs. Call 010 3532188 8231. Access, Visa, Mastercard.Eurocard. 455

CIRCOLECTHE COMPLETE ELECTRONIC SERVICE

Artwork, Circuit Design, PCB Assembly, Test & Repair Service, Q.A.Consultancy, Prototypes, Final Assembly. Full PCB Flow SolderingService.Quality workmanship by professionals at economic prices.Please telephone 01-648 5886 for advice or further details.

TAMWORTH MANOR302-310 COMMONSIDE EAST, MITCHAM

,1391

PCBs MANUFACTUREDFor ygAir circuits

* No job too big or too smallSingle or double sidedReal professional finish

* Low cost * Delivery lto3weeks* Precision artworks/photography* 5 years experience

Talk to Graham Slee or Mark Fisher on

0226 200717gee ElectroProductscompletethe circuit.

Unit 4Gtanta 11.00 Indust.* Est...Cterwood RoadBafnIteySouth rats/we Sic ISEEr44nd

When replying to

classified advertisements,

readers are recommended

to take steps to protect

their interest before

sending money


SERVICES

G.W.M. RADIO LTD40 42 Portland Road. Worthing. Sussex.

Tel: 0903 34897

tiers Receivers lest equipment components etcPye pocketrone PFI TX units with battery and circuitsC12 inc pap En 13T Meters Type r Tester SA 90835V50V'250V DC 250V AC/50rnA500rnA5A DC Lowand high ohms nets trom 2AA batts C9 as pap Type2 I2D 19 ranges 1-250V DC 10.1.000V AC 3 ohmsranges plus 0 05-1A DC 20K ohms V DC 16 ohmsV AC £13 inc pop Type 3 SA 908314 electronic550'2505 DC 059 5 5A DC 2500 AC 3 1low ohms andIM ohm range £16 Inc pap All meter movementschecked and supplied with leather case and jai, leads

P.C.B. ARTWORK DESIGNSERVICES. All requirements from:- SS1DS 1 ML & Screens & resists circuit - logic(redrawing NR) to:- Usts, prototypes &static tests. Liaison W.R.T. observed errors,problems. D.F.Busk Hillsdale, Green Lane.Letchworth SG6 1'40(0462) 682154. 456

P.C.B's DESIGNED. Artworkcapacity available for singledoublesided, P.T.H. and multi -layer P.C.B.'s,also silk screens, solder masks, labelsetc. For C.A.D./Photoplot, artwork &photography, contact Mr. Williams. 49Westbourne. Honeybourne. Evesham.W,01, W1111 5PT Ti.l?0386 s:12 I 7,2

409

As fromSeptember issueClassified rates

will be!25 per scc.

Lineage £5.50per line.

Box No. £12extra.

TURN YOUR SURPLUS i.cstransistors etc. into cash, immediatesettlement. We also welcome theopportunity to quote for completefactory clearance. Contact COLES-HARDING & CO, 103 South Brink,Wisbech, Cambs. 0945 584188. (921

PRINTED CIRCUIT BOARDSsingle and double sided manufacturedto your specifications. We offer qualitand fast service (same day onprototypes) at very keen prices. Wesupply copperclad material cut to size.Artwork service available. MondoCircuits Ltd. 35 Grossenor Rd,Twirkinham, Middx. 01-891 5412 413

DESIGN. PROTOTYPINGand BATCH PRODUCTION

Simple assemblies, PCBs.modules, or complete units.

Wide range of circuit techniquesand power levels.

Support and advice serviceWe offer a careful professional

service. at a careful price.T & B Services.

18 Ashlin Grove. Lincoln. LN1 1LE.(0522)39708

Please telephone or write torFREE HELPFUL INFORMATION.

WANTED FOR CASH,SURPLUS AND

REDUNDANT BROADCASTEQUIPMENT

Particularly medium -wavetransmitters, FM transmitters,

studio links (STL), studiofurniture, affects, cartmachines, AA3 carts.

COMP SHOP HI -TECH311 LONDON ROAD

CAMBERLEY. SURREYTel: 0276 29219 404

BILLINGTON VALVESNEW VALVE& TRANSISTORS tiugerange stocked Rarities our speciality Phone toimmediate qLotation. on any type SAE forcatalogueUSED VALVES - Tested. working c lean. 28day guarante.. KT66 GEC a FICHE (MazdaCV4055) C3. 12E1 C6-90 CV4024 M Alard (WaalO ECC8I 18Co. CV4003 Mullard (sp-ecialECC82) 70p All excluding VAT We will buyvalves compete shop clearance etcUSED TEKTRONIX 465 DUAL TRICESCOPE - 1011MHz As new condition. worksperfectly. mitt probes and lid £750 deliveredexcluding VA!'NEW ELECTROLYTIC CAPACITORS - Goulc10.000 MFD w 50V. 18 7 Amp disci arge Specsalquality for computer use etc Usually C8 -C12Our price C4 VAT deliveredNEW AUTO 'RANSFORMERS - eg

In 0 115 200 210 220 230 240 25(Out - 115V Or 13 05A. or 200-2501 ar 7 5A

C25 deliverec excluding VATMany transformers in stock, constant voltage.autos. multdaps etc. etc. List available duringJuly or phone your enquiry1.000 resistors or 1.000 capacitors - C3 50 VATdeliveredMixed parcel of IC transistors relays...apacdors resistors. potentiometers switches.2 569 - C5 VAT delivered. 10Kg - CIO VATdelivered

Billington Valves, 39 Highlands Road,Horsham, W Sussex RH13 5LS.Tel: 0403 210729: Fax 0403 210108:Telex, 87271 PRODSS G.Callers welcome by appointment.We accept Barclaycard Govt and export orderswelcome

TEST EQUIPMENTFOR SALE & WANTED

Buyers and Disposal Officerscontact:

COOKE INTERNATIONALUnit 4, Fordingbridge Site

Ma n Road, BarnhamBognor Regis

West Sussex P022 OEBTel: 0243 685111 2

Stock iist available, send 50pto cover p&p.

179

'.thantity ot manuals sho w1,1' .130,11f0n/ orf'of000py service etc Sanyo 60W IC amps N.

sgh output negative -an generator [45. Audio &Hi generators 14 11 capacitors Vacuum pumpEN. Diffuswon pump 9311. Electrostatic voltmeter00. Ignition Analyser C39. AuloManual 35mmSLR camera C79. electronic flash CIO both usedin colour Photomicrography Hap power strop,scope with sync facility used in hqh speed andslow motion colour video 6 ttlm ecorong photo-graphy 1135. Calibration standard rex (unused)£12.50. Miniature Matsubshe motor generators£2.75, reversible output & rotation dacha speedcontrol etc I Miniature flash A detonator gener-ators single stroke. high speed return. integralgearbox with capacitance 6 auto smith N. handoperated LCR Bridge Centrifuge Record Oise)cumng machines EMI MSS & BBC,Grampan£100ee. Binocular ComParatorrstereo examina-tion equipment £55. Aircraft Radio Test Set 05.lonesabon chamber with 3 -stage ampliker £25.chamber only C20. Record chart recorder withinterchangeable mains and Clockwork dnves [99.Wayne -Kerr RF Generator 5-100 MHz (very com-pact) ShaoweigN Indust.' Balance [45. Muir.head Multi -Ratio RF Bridge £65. DensrlorneterC35. Binocular 6 Monocular rocrscopes 1 Re-cording Tape or NAB spools O. OscilloscopePhaserneter £69. Last few Bkie Steel Rocketsections 5 for £50. NOUSE ,LABORATORvSMALL FACTnny OrrtCF PRFNI,FS for sale in

040-376236

UK MADE HIGH QUALITYLOUDSPEAKERS AVAILABLE

Dome Tweeters, Dome Mid -Range,Woofers and Sub -Woofers.

Uniquely EngineeredAluminium Voice Coils

For further information, pleasephone: 0473 719212 ,

INTEGRATED CIRCUITS: Largequantities for sale guaranteed in makerspacking, Top quality Hitachi HM65256AP-20 pseudo static RAM, NEC D80C42Cprogrammable microprocessor, INTELP80088 CMOS microprocessor. SMCFDC765AC floppy disk controller. Theseare all from discontinued product of topquality manufacturer. Call 010 35321873304. 457

ADVERTISEMENTSSales

INDICATED

Quadrant House.

andON FORM

The Quadrant.

CLASSIFIEDUse this Form

PLEASE INSERT THE

To "Electronics & Wireless World" Classified

Rate £5 PER LINE. Average six words per line.Minimum £40 (prepayable).

Name and address to be included in charge ifused in advertisement.

Box No. Allow two words plus £11. Cheques, etc., payable to "Reed Business

Publishing" and cross "& Co." 15% VAT tobe added.

WantsBELOW

Sutton. Surrey SM2 5AS

for yourADVERTISEMENT

Advertisement Dept..

NAME

ADDRESS

REMITTANCE VALUE ENCLOSED

PLEASE WRITE IN BLOCK LETTERS. CLASSIFICATION NUMBER OF INSERTIONS


MATMOS LTD, 1 Church Street, Cuckfield, West Sussex RH17 5JZ.Tel: (0444) 414484/454377

COMPUTER APPRECIATION, 111 Northgate, Canterbury. Kent CT1 1BHTel: Canterbury (0227) 470512. Telex: 966134 COMPAP G

PLESSEY Model T24 V22./V22 bis MODEM. Compact. automatic modem featuring the latesttechnology and the highest possible data rate over the ordinary phone system Offers both V22and V22 bis compatibility 12002400 Baud operation with auto bit rate recognition. operation on bothordinary phone IPSTNI and private circuit (PC) auto call and auto answer. duplex operationallowing simultaneous transmission and reception of data at 2400 Baud in both directions over asingle phone line, compact size 19 9 2' 2 1 BT approved BRAND NEW £350.00VICTOR SpeedPac IBM PC ACCELERATOR Half -wide 80286 accelerator card for IBM PC andcompatibles With 8kbyte cache memory and 7 2MHz 80286 processor Offers AT:PersonalSystem 2 performance for a traction of the cost Runs up to 7 5 times faster BRAND NEW C199.00ITT SCRIBE III WORD PROCESSING SYSTEM Professional system originally selling ataround 06.000 without printer Now offered with software Included and a variety of differingoptions (including hard disc. comms etc) available This system is available from us ALLBRAND NEW at the cost of current budget systems. but with office -quality performance andfeatures With dual processor workstation ( TI 9995 and Z8OHI 12 green display with slowscrolling. 128kbytes RAM. dual 500kbyte SHUGART 5, a' floppy disc drives and comprehensivesoftware C290.00SAMURAI Model S16 computer 8086 based 128k true 16 bit machine with twin 8" NEC floppydisc drives (total 2.5 mbytes. IBM 3740 compatible). monochrome (green) high resolutionmonitor. 2 RS232 interlace. CENTRONICS parallelinterf aces and MSDOS with lull set ofmanuals We have now sold out of complete machines. but have about half a dozen withoutkeyboards available C95.00TOSHIBA Model T300 PC SYSTEMS 8088 (6MHz) based system with 192kb memory. 2, halfheight DSDD floppy disc drives each of 655kb capacity (unformatted). high resolution greendisplay 25 , 80 characters. RS232 and CENTRONICS parallel interfaces MS-DOS Ver 2 andT -BASIC are included together with a diagnostic disc and manuals We have low cost packagesavailable now, including Word processing. Spreadsheet etc BRAND NEW £295.00AS ABOVE. but with single floppy disc drive C249.00TOSHIBA Model T100 CP/M SYSTEM. With 64kb RAM dual 500kb 5' a floppy disc drives.serial and parallel interlaces. BRAND NEW C149.00MATMOS TERMINAL MATMOS PC with Ver 2 EPROM for terminal emulation Probably thelowest cost terminal available anywhere With set-up menu and with data rates up to 9600 BaudMachine is easily modified for split Baud rate operation 75/1200B. EPROM plugs into ROM socketaccessible from exterior Emulation is VT -52 compatible for cursor addressing. and for characterattributes as far as the MATMOS PC allows MICROSOFT BASIC is still available from thekeyboard (EPROM card on its own. 020.00. EPROM card with socket only for users ownEPROM 08.00 BRAND NEW C69.00HITACHI Model 305S/SX 3" disc drives With SHUGART compatible interface as for 5' 4drives Uncased 125K (single density) or 250K (double density). 40 track, 100 tpi. soft sector.3ms track to track time. standard 34 way edge connector. 12V and 5V powered (standardconnector) with overall 3 7W typical power consumption These drives have been tested by us onthe BBC with DES. on the AMSTRAD 6128 and on the TATUNG EINSTEIN. and are alsoknown to be suitable for the AMSTRAD 664 and as a second drive for the AMSTRAD 464.Single -sided. 250kb unformatted BRAND NEW Data cables are available from us tor theAMSTRAD 6128 and BBC at £7.50. and an installation pack including data and power cables withinstructions is available for the TATUNG Einstein at C12.00 C24.95CANON Model MD0220 TWIN 51/4' FLOPPY DRIVES. Cased BRAND NEW half heightdrives. double sided. double density. 80 track. 640kb capacity per disc Shugart compatibleinterface. without PSU. per pair . C99.50KIMTRON Model ADM 85H VDU 24v80 intelligent VDU with TELEVIDEO 920/925 emulationFeatures include. non-volative set-up with status line. auxiliary port. all Baud rates 50-19200Baud cursor addressing. etc 0185.00

DEC PDP 11/23 SYSTEM with DLV11-J quad serial interface. TANDON 8 floppy with MICRODE V ASSOCS Model MXV-21 controller. FWITSU 8 Winchester disc drive with DILOG00401 controller 256kb memory Contained in 2'19 rack units in portable carrying caseSupplied with XENIX operating system complete with all original manuals and distributiondiscs C1,385.00ATARI Model 1024 STF personal computer with Model SC1224 medium resolutioncolour monitor. With 1101 simulator plus all usual software Originally purchased 1987 and asnew £565.00CALCOMP Model 463 AO graph plotter C325.00TOSHIBA HIGH RESOLUTION COLOUR MONITOR IBM compatible with RGB inputBRAND NEW C169.00TOSHIBA LOW RESOLUTION COLOUR MONITOR IBM compatible with RGB input BRANDNEW £95.00APPLE PROFILE 5mbyte WINCHESTER disc drive for APPLE II computers Complete withProDos operating system aid additional interface for APPLE II C275.00FUJITSU Model M2230AS 51/4 WINCHESTER disc drive 6 66mbyte capacity unformatted16/32 sectors 320 cylinders With ST506 interface BRAND NEWDEC Model VT101 VDU with many features including non-volatile sel-up slow scrolling etc £150.00.DEC Model BA I 1 MF box power supply and 8 slot backplance for 0 -bus BRAND NEW C185.00ADAC Model 1822 128kbyte CMOS memory for 0 -bus With battery backup C175.00TEKTRONIX Model 7603 100MHz OSCILLOSCOPE MAINFRAME with CRT readout £590.00TEKTRONIX Model 7403N 60MHz OSCILLOSCOPE MAINFRAME £250.00TEKTRONIX Model 7A17 75MHz 5mV dual trace amplifier. C175.00TEKTRONIX Model 7A18N As above. but without CRT readout £150.00TEKTRONIX Model 7B53A 100MHz dual timebase 0295.00TEKTRONIX Model 7012 A/C) converter with M2 sample/hold module C550.00TEKTRONIX Model 5403/015 60MHz oscilloscope with 2 5A48 A 5E142 £750.00TEKTRONIX Model 5103/015 2MHz single beam storage oscilloscope with 2 - 5A18N and5B1ON £550.00HATFIELD INSTRUMENTS Type 2105 50 Ohm affenualor £40.00BRYANS Model 45000 UV recorder with 6 45001 amplifiers 1 mV/cm.50V/cm and chartspeeds from 1 mm/min-500mmis Timing line interval is adjustable from 0.02s -10s and RecordDuration 0 5s -20s With remote control facility C195.00TEKTRONIX Model 851 digital tester One knob lets you dial 22 functions 11 functionsmeasure timing two register plus and minus peak voltages three carry out DMM measurements

and one reads line voltage at the outlet the 851 measures its 4 input thresholds to adjust tothe logic levels of the equipment being serviced 5, 2 digit readout 35Mhz frequency/timing.autoranging etcHEWLETT PACKARD Model 59307A dual VHF switch DC to 500MHz 50 Ohm switch for HP -113 C185.00HEWLETT PACKARD Model 5045A digital IC tester with CONTREL H310 automatichandler With IEE interface and print out of test results either pass/fail or full diagnostic includingpin voltages at point of !allure With full complement of pin driver cards and complete withsubstantial library of mag card test programs for 74 series TTL and other ICs CONTREL handlerallows fully automatic tes ing of ICs which are sorted into 2 bins Price includes a secondHP5045A (believed fully operational) for maintenance back-up 01,950.00TEKTRONIX Model 577 SEMICONDUCTOR CURVE TRACER With 5 heads for variousdiodes and transistors In excellent condition £1,900.00TIME ELECTRONICS Model 9810 programmable power supply C190.00TIME ELECTRONICS Model 505 DC current source 0 05°. With leather case 075.00PLEASE NOTE'VAT 6 carriage must be added to all prices. Please enquire for details.'All new equipment is guaranteed for 6 months.


INDEX TO ADVERTISERSAppointments Vacant Advertisements appear on pages 764-767

PAGEAEL CrystalsAdcola Products LtdAdvertising Standards

Authority 760Airlink Transformers 700

Barrie Electronics 694Brigden Technology 749

Cambridge Kits 726Carston Electronics Ltd ....666,745Channel Micro Products Ltd 750Cirkit Holding Plc 669Computer Appreciation 768Crash Barrier 687Crotech Instrumentation Ltd 753

Display Electronics 714/715

PAGE726 E&WW Wall Chart 726669 E&WW Feature List 756

Electronic Brokers IFC,OBC

Field Electric Ltd 676Fluke (GB) Ltd Advert Card

GNC Electronics 694Golten and Verwer Partners 686Guyvale Ltd 686

Happy Memories 752Harrison Electronics 745Hart Electronics 749Henson, R. Ltd 700Henry's Audio Electronics 726

ILP Electronics Ltd. 686ICOM (UK) Ltd 745

E.A. Sowter 749EMS Manufacturing Ltd 752 Johns Radio 694

PAGEKestral Electronic Components

Ltd 756Lab -Volt 670Langrex Supplies 746Levell Electronics 687Livingston Hire 681MA Instruments 726Micro Concepts 720Microprocessor E ngi neeri ng 745Mikro Kit Ltd. 682

Number One Systems 700Nuvotem Teo 756

P M Components Ltd 724/725Pineapple Software 668Process Communicator

Loose insertQuart -hand 750RTT Systems Ltd 676Raedek Electronics 750

PAGERalfe Electronics 682Research Communication 668

Sherwood Data Systems 670Solex International 694Stewart of Reading 756Strumech Engineers 682Surrey Electronics Ltd 686

Taylor Bros (Oldham) 676Technomatic Ltd 758/759Telonic Instruments IBCThose Engineers Ltd 669,753Thurlby Electronics 752Triangle Digital Services 700

University of LeedsLoose insert

Webster Electronics 750Withers, R. Communication 753

Xen Electronics 760

OVERSEAS ADVERTISEMENT AGENTSFrance and Belgium: Pierre Mussard, 18-20 Place de la Madeleine. Paris 75008.United States of America: Jay Feinman, Reed Business Publishing Ltd., 205 East 42nd Street. New York, NY 10017 - Telephone (212)867 2080 - Telex 23827.

Printed in Great Britain by E.T. Heron I Print) Ltd, Crittall Factory. Braintree Road, Witham, Essex CM8 3Q0, and typeset Ey Graphac Typesetting. 181,191 Garth Road, Morden, Surrey SM4 4LL,for the proprietors. Reed Business Publishing Ltd, Quadrant House, The Quadrant. Sutton, Surrey SM2 5AS. Reed Business Publishing Ltd 1987. Electronics and Wireless World can be obtainedfrom the following: AUSTRALIA and NEW ZEALAND; Gordon & Gotch Ltd. INDIA: A. H. Wheeler & Co. CANADA: The Wm, Dawson Subscription Service Ltd., Gordon& Gotch Ltd. SOUTHAFRICA: Central News Agency Ltd; William Dawson & Sons (S.A.) Ltd. UNITED STATES: Eastern News Distribution Inc., 14th Floor, I 1 1 Eighth Avenue, NewYork, N.Y. 10011.


Low cost electronicmeasuring instruments.TFG 81FUNCTION GENERATORS.

from£115

TFG 8101 gives sine, square. triangular, puts and rampoutputs over 0.1 Hz to 2Mz with output voltages up to 20Vpk-pl,TFG 8104 - all the features.of the TFG 8101 with 0-10( %ampl tude modulation and frequency modulation0 + 10.4

TFC 1200FREQUENCY COUNTERS.

from£142

1

8 digit Frequency Counters' TFC 1201 10Hz-100MHz direct.TFC 1204 10Hz-80MHz dr-ect, 50MHz-650.41Hz with pre -scaler; TFC 1207 10Hz-80MHz direct, 50MHz-1000MHzwith pre -e cater.

TPS 2000/4000 SERIESDC POWER SUPPLIES.

from£98

Inexpensive DC Bench Ppwer Supplies wi h single or dualtracking iutputs or dual racking with fixes - 5 volt rail.Outputs DC to 30 volts orOC to 60 volts win output currents0-1. 0-2. 3-3. 0-6 or 0-10 imps. dependinc on model.

All prices + VAT

FUNCTION GENERATORS.

from£189

TFG 8111 -a combination Function Genera or andFrequency Cot rifer 0.1 Hz to 2MHz sine. scmare, triangular,pulse and ramp outputs. with a 100MHz 6 DV frequencycour.ter.

TFG 8114 - is -he TFG 8111, except 5 digit punter plusoutput frraqt ercies up to 5MHz and sweep, rigger, gate andburst functi

TFG 1210 UNIVERSALCOUNTER TIMERS.

from£187

8 digit Univer!al Counter timers with frequency. period,inte-val, rev) and totalise functions. TFC 1211 5Hz-100MHzdirect. TFC 1214 5Hz-100MHz direct, 50Mrlz-650MHz withpre- scaler;TF: 1217 5Hz-100MHz direct. 5DMHz- 1200MHzwith pre-sc aler.

TPS 2000D/4000D SER ESDIGITAL DC POWER SUPPLIES.

from£130

a.

I 14.

41.441alal

Similar to he TPS 2000/4000 range but wth digital voltageand currer t measurement. Digital meter czn also be used asDVM

TopwardElectronic Measuring Instruments

1

FUNCTION GENERATOR.

£549

TFG 4613 offers sine, square, triangular, ramp. pulse, A.M.,FM., =weep, trigger, gate, burst over 0.1Hz to 13MHz at upto 20v' pk-pk. Amazing value,

TOM 100 SERIESDIGITAL MULTIMETERS.

from£152

LN10'

il-17111111 ad)

TM 104 - 3'h digit Bench Multimeter with 1(1 % 1

digit accuracy. Measures DC 8 AC volts and ct rrent andresigance. High 1000M I1 impedance.TM, 105 - 4'h digit true RMS Bench Multimeter with± (02,4% + 1 digit) accuracy. DC 8 AC voltage and currentplusaesistance measurement.

AC MILLIVOLT METERSTMV 300 SERIES.

from£94

TM / 360 -a single channel AC Millivoltmeter with f.s.d.ran.ges from lmV to 300V and bandwidth 10H: to 1MHz.TM / 380 -a two channel instrument. f.s.d. rar ges 1 Mv to30CV and a 10Hz to 500KHz bandwidth.TM 1381 - also two channel, but f.s.d. ranges 31313µV to 100Vanc 5Hz to 1MHz bandwidth.

Telonic nstruments Ltd.Boyn Valley Road.

Maidenhead,Berks. SL6 4EG,

England.Tel: (0628) 73933

Telex: 849131Fax (0628) 770529

IENTIKII 2 ON 11E1'1,1' EA It I)

ELECTRONIC BROKERS

PHILIPSPM3302Real time or digitalstorage, withsampling rate20MHz, maxresolution 5Ons,2k x 8 bit memory,2 channels. WithIEEE option £2125.

PHILIPSPM325675MHz, compactruggedised portablescope with shoulderstrap, dual trace,2mV sensitivity,delayed time base,trigger view, 111triggering.

HAMEGHM60560MHz, dual trace,sweep delay,maximum sensitivityI mV, versatiletriggering,Z modulation, X -Yoperation, in-builtcomponent tester.

£583

PHILIPSPM3055

The world leader in 'scope technology', this 50MHzoscilloscope with true dual timebase offers features that makeit the smart choice for performance and simplicity.Features: True dual timebase, calibrated sweep delay, 16KVacceleration potential CRT, third channel (Trigger view),autoset of amplitude, timebase and triggering, SPECIALLCD panel, easy to use front panel design. OFFER

HAMEGHM205Real time to 20MHz,digital storage to10KHz, 1024 x 256point resolution onX and Y axes, singleand refresh modes,active video trigger.

GRUNDIGM02220MHz, dualchannel, automatictimebase selection,triggerable secondtimebase, hold -offcontrol andZ -modulation,TV triggering.

£499

HAMEGHM203-620MHz, dual trace,2mV/cm maximumsensitivity, componenttester, add andinvert, automatic andnormal triggering,X -Y operation, with2 probes.

£314

Also Available . 15MHz dual traceT 1handar TO315 5MHz battery porte £780 Phiii pmn?nAPhilips PM3267 100MHz dual traceabl£1627 Hameg HM208 20MHz D.S.O.

£350£1460

UK's No.1 Test Equipment Distribution Company0 Lif, 0

i7Electronic Brokers

L'=" Electronic Brokersn- -1 n- 140/146 Camden Street, London NW1 9PB= U Fax: 01-267 7363. Telex: 298694. Tel: 01-267 7070.

All prices exclude VAT and carriage and are correct at time of going to press. ry it 3 (iN tAlt1)

& wireless world...tf 2604 voltmeter £425 tf 2702 inductor analyser £950 tf 2905/8 tv pulse...

Documents