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ETI for Electronics & Computing Enthusiasts

INTERNATIONAL

Middle to high -end

5 74 3 8

Sord Soclus M5Computer

Review

December 1983

$2.75MM70924

EXCELTRONIX(416)921-89411-80Bulletin Bd. (416) 921-4013 Telex 065-24218Catalog shipping rates are incorrect. Please call us for correctcharges.

monitorsogi Zenith ZVM-122 Amber $195

Zenith ZVM-123 Green Amdek Colour -1 53955129 Amdek Amber - 300A 5259

8-3798Multiflex

intelligentTerminal

(As Reviewed in Oct. '82 ETI)An excellent low costterminal kit from $195

Assembled & Tested withcase and PIS

$350

MintifieX lay $995Super System-S100 Based-Z-80A Processor-runs CP/M-EPROM ProgrammerBASIC Package includes-CPU card w. 64K-Video BoardDisk Controller-SA455 Drive-CP/M Operating SystemOPTIONS

Power Supply: 5V 4A,12V 2A, -5V 0.5 A, -12V0.5A $99Keyboard(no case) $99

Memory Chips4164 - 150 ns (1x64K single (+ 5V)supply)4116-200ns (1x16k)4116-150 ns (1x16k)2114L-200 ns (1kx4 static)6116-150 ns (2kx8 static RAM)(Pin compatible with 2716 uses negligibleamount of power)2016-150 ns (2kx8 static)2102L-200 ns (1 kx1 static)5101-CMOS RAM2708-(1kx8) EPROM2716-(2kx8 EPROM single + 5V)2732-(4kx8 EPROM single + 5V)2532-(4kx8 EPROM single 5V)2764-(8kx8) EPROM single 5V)

8.441.741.992.498.94

8.741.943.846.744.947.948.74

1t94

Ifs

UI

WE NAVE ASPECTACULAR

STOCK OF74LS PARTS

ATREASONABLE

PRICES.OEM

ENQUIRIESINVITED

Featuring theMuItIfIex Apple~Compatible Driv1 YEAR WARRANTY1000'5 SOLDAN EXCELLENTCHRISTMAS GIFTIDEA

PRICE POLICYRemember that at Exceltronix allprices are negotiable for quantitypurchases. If you cannot afford largequantities on your own how aboutstarting a Co-op.

Diskettes51/4" Diskettes Boxes of 10Maxell MD -1 $36.00Maxell MD -2 $52.95Verbatim $34.00CDC $27.95Dysan $33.953M $32.95Ectype (with library case worth$4.95) $27.442 Ectype Diskettes in a plasticbinder sheet $5.89SPECIAL Free calculator when youpurchase 5 boxes of 3M diskettes.

only$269

JoysticksSelf -Centering S39.95With two adjustable controlsSuper offer

Kraft Joystick

TG JoysticksDeLuxe Model

TG PaddlesDe Luxe Model

$69.00

$75.00$64.95

Deluxe Table Top Model559.00

Also available at $299with 90 day warranty!

a. Teac Slim Driveb. Micro-Sci DriveSA400L Mechanismc. Quentin DriveSiemens Mechanismd. ATI FDD-810 Slim Type

Controller $89Coming SoonCommodore & IBMperipherals!

MAIL ORDERSSend a certified cheque or money order (do not send cash). Minimumorder is 510 plus $3 minimum for shipping. Ontario residents mustadd 7°.0 provincial sales tax. Visa. Mastercard and American Ex.press accepted: send card No . signature. expiry date and name ofbank.

Head Office: 319 COLLEGE STREET, TORONTO, ONTARIO. CANADA. M5T 1S2 (416) 921.8941Circle No. 7 on Reader Service Card.

BEFORE YOU BUY ANY IBM COMPATIBLEPRODUCTS; CHECK WITH US FIRST. FOR BEST

PRODUCTS AND PRICES.1-800-268-3798 (416) 921-8941 Telex 065-24218

EXCELTRONIX wishes you a Merry ChristmasSiDEACOOlg"

November Software Specials Witness .............. $42.95 Locksmith $125.00 NEW Book SpecialsSea Dragon $41.00 DOS Tool Kit $89.00

Castle Woltenstein $34.95 Evolution $39.00 Apple Software 1983 $22.00Wizardry $47.95 Apple Panic $36.00 Crosswire $36.50 The Blue Book $26.95Knight of Diamonds $36.97 Frogger $41.00 Screen Writer II $159.95 CP/M Assembly LanguageUltima!! $64.95 Flight Simulator $48.00 Lisa $119.95 Programming $15.00Pinball Construction $42.95 Pinball $39.00 Zaxxon $49.95 The Power of Multiplan $17.95Suspended $46.95 Fork I $39.00 Computer Baseball $39.00 A User Guide to the Unix System $20.00Chess, Odesta $74.95 Deadline $48.00 David's Midnight Magic $39.00 Motorola CMOS Data $12.95Cosmic Balance $39.95 Ulysses $47.00 Typing Tutor II $24.95 Motorola Linear Data $12.95Miner 2049'er $38.95 Temple of Apshai $46.50 Flip 'n File 50 $39.00 TTL Data Book $14.00

StramicronicsincGemini 10X81/2", Dot Matrix,80 Column, 120c.p.s. Regularprice $615.

PRINTER SPECIALSGemini 15X 569915", Dot Matrix, 132 column, 100 c.p.s.

E PSON MX8OFT 579581/2", Dot Matrix with GRAFTRAX +

E PSON MX100 $99515", Dot Matrix with GRAFTRAX +

I EPSON RX80 (NEW) $495Replaces MX80

PAPER 510.45For your printer

Control Data, 91/2" x 11" plain, 500sheets Other sizes available.

RF MODS 518.00Applesoft Tutorial $14.44DOS Manuals $25.00

SA455 Disk DriveHalf Height, Double Sided,IBM Compatible 5349

EMP Mini Modem300 Baud, Direct Connect Regular Price $199

Special Price $124

Smart Modem300 Baud, Direct Connect

Special Price 5399

Micro Modem 5459300 Baud, Direct Connect Plugs into Apple1M

EPSON FX80 (NEW) 579881/2", Dot Matrix, 80 column, 160 c.p.s.

TTX PRINTER 5789Daisy Wheel

PDA-232 RS232 $119.00

WIZARD BPO-16, Apple $184.00Compatible16K parallel buffer printer card

Wizard - IPI parallel intelligentprinter interface $85.00

5" Green ScreenSync SeparatorKit$9.95

Open frame.Requires 12V.Ideal for 6502computers.

Requires SyncSeparator Board

CHRISTMAS GIFT CERTIFICATES AVAILABLE.AN EXCELLENT GIFT FOR THE COMPUTER ENTHUSIAST!

Monitors$59

16K RAM Card

$55.00Expand you 48K APPLE to 64K. TheMULTIFLEX 16K RAM Card allows otherlanguages to be loaded into your Applefrom disk or tape. Allows APPLE CP/Musers to run CPIM 56.

CRARGEX

EXCELTRONIX

Multiflex EPROMProgrammer $69FEATURES:*EPROM programmer for APPLE com-puters.`Programmes 2716, 2732, 2732A, 2764.*ZIF socket for the EPROM.*Complete with software.`Built-in programming supply.

We have a large selection of books andmagazines

PROTO BOARDS 514.00

80 -Column CardFEATURES:`Gives 80 columns and upper/lower caseon your APPLE II/II + /Ile computer.*Works with PASCAL and CP/M.'Auto -switch between 40 columns and 80columns.*Full inverse video. 574

Z-80 Card'Runs CP/M on your Apple`You can run hundreds of professionalsoftware packages

*Software not included. $58

Exceltronix Computer Division Computers at unbeatableprices! (416) 921-8941, 319 College 5t., Toronto, Ontario

11,15T 152No returns or exchanges after 7 days. 15'7 restocking charge.

Circle No. 7 on Reader Service Card.

SURPLUSTRONICSAS

Rev/owedIn IMMUY11983

64K RAM (8-4164 chips)80 x 24 video included on boardFloppy Disk Controller IncludedFIVE additional slotsZ80 blank PCB IncludedPowerful power supply (5V 59, + 12V 2up to 3A peak, - 5V OSA, -12V 0.5A)Hydro -approved whereas many others

are not! Superb quality plastic case Excellent keyboard including numeric

keypad EPROMS (blank) included

we will not be undersold

OUR FAMOUS 6502/80886 502 BOARD BoardNOW NEW & IMPROVED VIDEO SECTION

This 6502 board is a vast improvement on others available: High QUALITY pc board Excellent service Now at a reduced price $599 kit

Available in Kit. Availablepreassembled (with all sockets, conn,& discrete, flow soldered & cleaned.IC's to be inserted by user not tested)

only $29. on top of kit cost.Complete assembled & tested

(blank EPROMS $689

NOW you receive a FREE Z80 PC BOARD ANDFREE 128K RAM DISK PC BOARD when you orderthe complete package (either Kit or A&T) (BLANK

CALL FOR PRICING

We have the Best Prices onIBM Peripheral Boards andCases. Also our own 8088Boards with mostPeripherals on Board. Checkwith us before you buyanywhere else.

CALL FOR PRICING

HOW8088 BOARDCOLOUR GRAPHICS256K RAM or 1MEG. usingnew 256K RAM Chips. Floppy controller 110 And muchmore Sold with all parts includingblank EPROMS Compatible with ???Yes you guessed It. At a price so lowyou won't believe it. Please call forordering & pricing. Demand is overwhelming. Orders will be filled (On afirst come first served basis).

TO BE RELEASED OCT. 30

CALL FOR PRICES

5" Green ScreenMonitors. $59

Open frame.Requires 12V.Ideal for 6502computers.

Requires SyncSeparator Board

KIT $9.95Peripherals for your APPLE Vag

16K RAM Card - complete A&T $55.00

Eprom Programmer- A&T with $69.00software to program 2716, 2732, 2732Aand 2764.

Z80 Card - (no software) A&T

80x24 Video Board(runs CP/M & Pascal)

Wizard Printer Interface card with Epsonpersonality Eprom (works great withGEMINI 10X) Complete $79.00

Our own Printer interface card A&Twith blank personality Eprom $49.00

128K RAM Disk A&T (no software)$199.00

$57.00 APPLETM Compatible Disk Drives attrac-tively packaged, ready to plug in

$73.00 $269.00

Disk Drive Controller A&T $79.00

Our Disk Drive Controller, A&T, with twoblank 2716's $49.00

GEMINI 10X Printers $359.00

Wild Card provides back-up copies ofprotected software with just the push ofa button $139.00

Our Crazy Card provides back-up copiesof protected software with just the pushof a button only $59.00

PDA 232 $118.00

Huge variety of Surplus stock at low, low prices. Newshipments arriving. No reasonable offers refused.

Mail Orders add $3.00 minimum for shipping &handling. Ontario residents add 7% P.S.T. Visa,Mastercard and American Express cards accepted: send card number, expiry data, name ofbank and signature. Send certified cheque ormoney order, do not send cash.

This month only, we will ship free of chargeto Ontario Residents only.

Circle No. 22 on Reader Service Card

Surplustronics, 310 College Street, Toronto, Ontario, M5T 1S3 (416) 925-8603.1-800-268-3798 (416) 925.6558

The Magazine for Electronics & Computing Enthusiasts

Electronics December 1983Vol. 7 No. 12ISSN 0703-8984

Member

Audit Bureauof Circulations

FeaturesElectronic Mail01 Will high-tech eliminate getting envelope glue onyour tongue? Roger Allan reports onsatellite.

15

26

Which Battery To Use?If your flashlight goes dead too soon, light acandle and read this guide to selection.

50 More ComputersWe continue last month's survey with a lookthe jazzier but pricey high -end models.

34383945

Designing Microsystems, PartThe bootstrap start-up.

Product ReviewThe Brother EP -20 Electronic Typewriter.

Computer Review: Sord Socius M5Rubber keys meet dynamite BASIC graphics.

Designer's NotebookVoltage multipliers: get a 250,000 volt lightningblast from a hearing aid battery. For those whodare.

50 Nuclear Applicationsin ArchaeologyRoger Allan presents a scientific examination ofpottery from the grave and skeletons from thecloset.

6468

Computing TodayVIC-20 Graphics Listing.

Book ReviewMathematics for Electronics.

Projects20

23

NiCad Charger/RegeneratorDon't throw out those apparently dead NiCads.Chances are they can be revived with thisproject.

Expanded Scale VoltmeterKeep an accurate eye on battery packs andpower supplies with this 10 to 15 V meterproject.

Our CoverVarious batteries and relatedcircuits are covered in thisissue; photo by Bill Markwick.The Sord M5 is reviewed on page39; photo by the UnknownEditorial Assistant.

45

ADVERTISERS' INDEX

Active Components Sales Corp. 65Allan Crawford & Associates 76,77A.P. Products 80Arkon Electronics 71Audiovision 17BCS Electronics 37Brunelle Instruments Inc 35C&H Electronics Plus 12

Daetron 32Electronic Control Systems 65Electronic Packaging Systems 35Exceltronix 2 3Fastron 33Fujicomp Inc 75General Electronics 49Gentek Computers Inc 32H. Rogers Electronic Instruments 54Innovative Electronics & Devices 21Interfax Systems Inc 79l&S Software Library 65JLS Computers 49JMT Inc. 49Kitstronic International Ltd. 24McGraw Hill 29Metermaster 44Micro Computech Electronics Ltd. 40,41Nielsen Computers Inc 47Orion Electronic Supplies 8 9Parts Galore 22,69Protec Microsystems Inc. 72Sallelite Systems Ltd. 65Surplustronics 4

NEWSSTAND DISTRIBUTION:Master Media, Oakville, Ontario

SUBSCRIPTIONS$18.95 (one year), $33.95 (two years). For US add$3/yr., other countries add $5/yr. Please specify ifsubscription is new or a renewal.

BINDERSBinders made especially for ETI are available for$9.25 including postage and handling. Ontarioresidents please add provincial sales tax.BACK ISSUES AND PHOTOCOPIESPrevious issues of ETI Canada are available directfrom our offices for $4.00 each; please specify bymonth, not by feature you require. See order card forissues available.

We can supply photocopies of any articlepublished in ETI Canada; the charge is $2.00 per arti-cle, regardless of length. Please specify both issueand article.

COMPONENT NOTATION AND UNITSWe normally specify components using an interna-tional standard. Many readers will be unfamiliarwith this but it's simple, less likely to lead to errorand will be widely used everywhere sooner or later.ETI has opted for sooner!Firstly decimal points are dropped and substitutedwith the multiplier: thus 4.7uF is written 4u7.Capacitors also use the multiplier nano (onenanofarad is 1000pF). Thus 0.1uF is 100nF, 5600pFis 5n6. Other examples are 5.6pF = 5p6 and 0.5pF= Op5.Resistors are treated similarly: 1.8Mohms is 1M8,56kohms is the same, 4.7kohms is 4k7, 100ohms is100R and 5.60hms is 5R6.

Playmate Part 2In which we finish upconstructional detailsof this instrument ampand (blush) correct anerror in the originalschematic.

Columns, News andInformation

For Your Information .. 6 Order Form 55Next Month 19 Subscriptions 56

ETI Specials 73Fun of Electronics 66Classifieds 74ETI Binders 78ETI Bookshelf 57Tech Tips 71

PCB SuppliersETI magazine does NOT supply PCBs or kits but wedo issue manufacturing permits for companies tomanufacture boards and kits to our designs, Con-tact the following companies when ordering boards.

Please note we do not keep track of what isavailable from who so please don't contact us for in-formation on PCBs and kits. Similarly do not askPCB suppliers for help with projects.

K.S.K. Associates, P.O. Box 266, Milton, Ont. L9T4N9.B-C-D Electronics, P.O. Box 6326, Stn. F,Hamilton, Ont., L9C 6L9.Wentworth Electronics, R.R.No.1, Waterdown,Ont.,LOR 2H0.Danocinths Inc., P.O. Box 261, Westland MI 48185,USA.Arkon Electronics Ltd., 409 Queen Street W., Toron-to, Ont., M5V 2A5.Beyer & Martin Electronic Ltd., 2 Jodi Ave., Unit C,Downsview, Ontario M3N 1H1.Spectrum Electronics, 14 Knightswood Crescent.Brantford, Ontario N3R 7E6.

POSTAL INFORMATIONSecond Class Mail Registration No.3955. Mailingaddress for subscription orders, undeliverablecopies and change of address notice Is:Electronics Today International, Suite 601,25 Overlea Blvd., Toronto, Ontario, M4H 1B1.

ETI-DECEMBER-1983-5

for your information_

ETI Magazine is Published by:

Moorshead PublicationsEditorial and Advertising OfficesSuite 601, 25 Overlea Boulevard,Toronto, Ontario, M41-1 1B1Telephone (416) 423-3262

Publisher: Halvor W. MoorsheadEditor: Bill MarkwickEditorial Assistant:Anthony DeBoerProduction Manager:Ann RodriguesProduction: Susan Cross

Robin Mills -O'NeillDoug Goddard

Earl GunawardenaCirculation Manager. Lisa Salvatori

Accounts Department: Pirjo DunphyAdvertising: Omar VogtRepresentatives: Rick MayAdvertising TrafficCo-ordinator: Claire ZyvitskiAdvertising Services: Carolyn Wyatt

Sharon CerneccaGeneral Manager. Senga HarrisonExecutiveVice -President: V. Kenneth Marskell

COPYRIGHTAll material is subject to worldwidecopyright protection. All PCB patternsare copyright and no company can sellboards to our design without our permis-sion.

LIABILITYWhile every effort has been made to en-sure that all constructional projects refer-red to in this magazine will operate as in-dicated efficiently and properly and thatall necessary components are available,no responsibility whatsoever is acceptedin respect of the failure for any reason atall of the project to operate efficiently orat all whether due to any fault in thedesign or otherwise and no responsibilityis accepted for the failure to obtain corn-ponent parts in respect of any such pro-ject. Further no responsibility Is acceptedin respect of any injury or damage causedby any fault in design of any such projectas aforesaid.

Editorial QueriesWritten queries can only be answeredwhen accompanied by a self-addressed,stamped envelope. These must relate torecent articles and not involve the staff inany research. Mark such letters ETI-Query. We cannot answer telephonequeries.

PC Bubble CardEcoSea Technologies Corp. has an-nounced the release of the world'sfirst magnetic -bubble memory cardfor the IBM PC and IBM PC -XT.

The Pure Data PDIBI28 andPDIB384 provide either 128K or384K respectively, of non-volatilememory storage using only one slotof the IBM backplane. Unlike afloppy disk, the cards are entirelysolid-state, with no moving parts.This means that the devices are im-pervious to dust, dirt, fumes orvibration.

Another first is the feature ofpassword protection in hardware.The end users can create their own

Commodore Computer is host-ing The World of Commodore at theInternational Centre in Toronto,Canada on December 8-11 to markits 25th anniversary. This isCanada's first truly internationalcomputer show, involving hardwareand software exhibitors and seminarspeakers from 10 countries includingWest Germany, the United King-dom, Japan, Sweden, France, HongKong and the U.S.A. It is also thefirst major consumer exhibitionmounted by a single manufacturer inCanada.

Chopper AnalyzerHelicopter maintenance time can besignificantly reduced by a British in-strument which is capable of analys-ing rotor performance and offeringbalance corrections in flight. Elim-inating the dangerous, time consum-ing and often inaccurate conven-tional methods of assessment, themicroprocessor -based Rotortuneruses a low -power short-range radarunit on the body of the helicopter tomeasure damper performance andblade position. Variations in heightand angular displacement are dis-played at each selected flight speed.These findings analyse during flightany necessary adjustments to bemade to the weights on the bladetips, blade bolts, balance points orblade sweep. As the instrument in-cludes a memory, findings can becombined with known characteristics

password to provide the ultimate insecurity for their PC system. Oncecreated, the password can be used to"lock -up" either the computer itself,the bubble card only, or both de-vices. This password protection can-not be bypassed by any means, andno method exists to "read" thepassword.

Used as a virtual disk drive, thebubble card is many times fasterthan a floppy disk drive, and muchmore reliable. The bubble card oper-ates as a standard DOS 2.0 disk -typedevice, is compatible with all DOSsoftware, and does not require anypatching of system files. ThePDIB128 and the PDIB384 use two

of the system, with a trend analysisfrom one servicing to the next andwith data from other aircraft in theproduction series. It can then recom-mend the maintenance test pro-cedure to be adopted. By additional-ly providing a logical sequence forthese tests to be carried out and alsoeliminating any need for reference todata tables and charts, it further re-duces maintenance time.

The analyzer is marketed byHelitune Ltd., 16a Reading Rd.

I/O lines and no memory space.Both DMA and interrupts are sup-ported, but not required.

Comprehensive diagnostic soft-ware and other utilities are providedfree of charge with the card, alongwith a full illustrated installation andoperation manual.

EcoSea Technologies Corp.,465 King Street East, Unit 13,Toronto, Ontario M5A 1L6 (416)366-1000 is Canadian distributor forthese and other products manufac-tured in Canada by Pure Data Ltd.

South Fleet, Hampshire, EnglandGU13 9QL Telephone: Fleet (02514)4798 Contact: David Bloxham,Commercial Director Enquiries frompotential customers/agents are wel-comed by the company.

6-DECEMBER-1983-ETI

For your irilorniatioriAmerican Telephone & Tele-

graph Co. is planning to introduce amicrocomputer system within thenext six months, according to a new237 -page research report from Inter-national Resource Development Inc.The report predicts that the micro-computer will use 32 -bit architecturebased on Western Electric's Bel!macmicroprocessor, and that the soft-ware will be based upon Bell Labora-tories' Unix operating system. Thecombination of the longer wordlength (32 bits, as compared with 16bits on the IBM Personal Computer)and the powerful Unix -based soft-ware, will enable the new AT&Tmicrocomputer to "upstage" theIBM PC, according to the report.

AT&T will have difficultycatching up with IBM's lead becauseof the accelerating production ofPCs. "We are aware of specific IBMcomponent and sub -system contractswhich point to definite productionplans for two million PCs in 1984,"says the report, which states thatAT&T will be "lucky if Western canmanage to make 30,000 of theAT&T micros in 1984."

Bell Laboratories has received its20,000th patent. World famous asthe research and development arm ofAT&T, Bell Labs has averaged near-ly a patent a day since its founding in1925, with innovations includinglong-distance TV transmission in the1920's, microwave radio transmis-sion in the 30's, the transistor in the40's, semiconductor electronics inthe 50's, communications satellites inthe 60's, digital switching in the 70's,and lightwave transmission in the80's.

The 20,000th patent - anotherlightwave innovation - is for a newtechnique, using a gas to etch ex-tremely smooth surfaces on semicon-ductor compounds which offer ad-vantages over silicon for manydevices. The ultra -smooth surfacesare of particular interest for use intiny lightwave circuits comparable totoday's electronic integrated circuits.

The Bank of Montreal has com-mitted to become the first multi-national corporation to use Tele-globe Canada's new internationalprivate satellite business services. Us-ing a small 4.5 m earth station anten-na mounted atop the 72 -story FirstCanadian Place building in Toronto,Teleglobe Canada will provide theBank with a highly reliable and cost-effective integrated digital communi-cations network, initially between theBank's offices in First CanadianPlace and Bucklersbury House, Lon-don, England. The service is schedul-ed to begin in January.

New Trim Pots

Preh has just released its new Trim-ming Potentiometer for P.C. boardmounting and automatic insertion.Measuring 8.6 mm, it is available inbakelite or Cermet and is completelywashable. The wiper assembly isshroud protected and the actuatorhas an inside taper to accommodateautomatic adjustment tools. Achoice of hex or cross slot actuatorsis available, allowing adjustmentfrom either the top or bottom.

For further information, pleasecontact Atlas Electronics, 50Wingold Ave., Toronto, Ont. M6B1P7 (416) 789-7761.

The world's first regular broad-cast service of computer programs -Telesoftware - is to be started inBritain by the BBC this year (1983).Test transmissions have already beenbroadcast.

Most of the early programs willbe educational ones, intended mainlyfor use in schools and colleges. In-deed, one of the major suppliers willbe the British Government's $20million Microelectronics EducationProgramme, which was set up totrain teachers and provide software.Later a full range of programs willbe transmitted, for home and busi-ness applications, and there will alsobe video games.

Tingle FilterElectricians and contractors in ruralareas should recognize the profitpotential of this newly developedTingle Voltage Filter for applicationson farms where stray or tingle vol-tage related animal productivitydeclines are a problem. Tingle vol-tage or stray voltage is a pheno-menon resulting from small electricpotential, usually 2 to 3 volts, beingpresent between grounded metalfarm equipment (such as wateringtroughs, feeders, metal penworketc.) This potential causes many be -

New PCB DIN'sPreh, a leading manufacturer ofDIN connectors for computer andtelecommunications applications,has introduced a new line of recep-tacles that permits peripheralgrounding of the inserted connectorshell.

The aspect of a reliable groundconnection between the DIN recep-tacle and cord plug is important dueto R.F.I. problems in computer ap-plications. The grounding alsoeliminates the problems associatedwith static electricity.

Preh, is now represented inCanada by Atlas Electronics Limit-ed, 50 Wingold Avenue, Toronto,Ontario, with branch offices in Mon-treal, Ottawa, Winnipeg, Calgary,and Vancouver.

For further information or tocontact: Bruce Petty, at (416)789-7761.

havior problems in farm animalswho come in contact with the equip-ment.

Most farms will have some de-gree of tingle related problems,which can result in many problemsto the farmer; milk productivitylosses, breeding problems, mastitis,pig scours, and general stress reac-tions are common.

Until now, the only solutionswere expensive or even dangerus:separation of the primary neutralline from the barn neutral greatly in-creases danger from lightning andcan create safety problems; isolationtransformers are a good solution butare very costly; equi-potential gridsystems are only viable in new barnconstruction.

The Tingle Voltage Filter isabout $300, and is easily installed atthe main pole or at the main barnpanel. It will reduce tingle voltage tobelow 0.2V in most areas. This iswell below the threshold of dairy cat-tle and other farm animals.

Contact: Hammond Manufac-turing Company Limited, 394 Edin-burgh Road North, Guelph, Ont-ario, Canada N1H 1E5.Telephone: (519) 822-2960 or (416)456-3770.

ORION ELECTRONICS COMPUTER ROOM ORION ELECTRONICS COMPUTER ROOM

WINNER: Ultra -modern!Super -efficient!Please note the distinct featuresWinner offers:*Dual microprocessors 6502 & Z -80A'RS -232 built in'Disk drive interface card built in'40/80 column text display and auto change videooutput port by soft switch

76K RAM with 4 expansion slots'16K ROM'DOS 3.2 & DOS 3.3 capability 'Upper/lower case*Apple & CP/M compatible 'Streamline case*ASCII keyboard with function keys and a numeric *OS could be changed when desired without affectingkeypad other memory RAM

$995

"ADD VISION TO YOUR COMPUTER WITH THE MICRON EYE"- solid state - programs included - hardware, software & optics

included, $449.00Roland CB- 1 41

COLOR B

$449.00

Composite System Colour Display

Composite system, 14 -inchdisplay.

With its built-in amplifier andspeaker, it accommodatesgames, video monitor, etc.

Low cost but provides highperformance with sound circuit& headphone jack.

Protected from an erroneousoperation of a floppy disk driveunit and dealt with a shieldtreatment for a magnetic inter-ruption against other electronicunits.

Electrohome Monitors& Accessories

EDM926/B&W9" Black & White monitorEDM926/P319" P31 Green MonitorEDM1226/B&W12" Black & White MonitorEDM1226/P3112" P31 Green MonitorECM1302.113" Color RGB MonitorECM1302-2 $450.0013" Color RGB Monitor Hi Rez.1-1302 $ 69.50NTSC Interface for ECM1302 for Apple II Computers(1 year warranty from Electrohome)MP -1302 -APL $199.00RGB Card for Apple II or Franklin 100Zenith 12" Green $139.0012" AmberA MDEC-1 Colour 13"MACKINTOSH12" Amber

$159.50

$169.50

$179.50

$189.50

$389.00

$169.00$398.00$169.95

TTX" 1014RELIABLE DAISY WHEEL RO PRINTER

$7491014 FEATURES SERIAL AND PARALLEL

INTERFACEII WORD STAR' COMPATIBLE QUIET OPERATION

III PROGRAMMABLE PITCH AND INTEGRAL PIN FEED GLINE SPACING (ADJUSTABLE)

COMPACT AND DURABLE RIBBON CARTRIDGES AND MICRO, MINI, MAINFRAME PRINTWHEELS READILY

COMPATIBLE AVAILABLE

Also Available The CP80 DOT MATRIX $495. Same as Epson 80.

UIDE

Assembled$58.00ZX81Printer$119.0016K Sinclair Memory

$59.00Books Hardware

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tapesNOT ONLY 30 PROGRAMS IX 16.CHINE LANGUAGE MADE SIMPLE ISZX8I ROM DISASSEMBLY PART A PART B 24UNDERSTANDING ZOO, ROM 19TIN ICON PROGRAMS, GAMES andGRAPHICS 1

LEARNING 10 BASICTHE BASIC HANDBOOK49 EXPLODING GAMESCOMPUTER FOR KITS SINCLAIR EDITIONMASTERING MACHINE CODE ON TOUR MI 241.TIS 17420 USERS GUIDE Plot I/ 16EXPLORERS GUIDE TO THE ZXIII 111

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THE ORION II 64K COLOUR COMPUTER $495.00 0064K with dual Basic, Apple Soft & Integer BasicORION II

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ORION IIISame as Orion II, plus upper and lower case withnumeric keypad with multi function keys .. . . $595.00

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Orion II $995.00Orion III $1,095.00

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AMB.1 $325.00

Mother Board, APPLE II Compatible, Assembled &Tested c/w Basic ROMS, 64K RAM, Made in Japan, In-teger & Reg Basic.ABB-1 39.00APPLE II Compatible, Motherboard (no components)6502 Board Kit $250.00Includes all partsAEI3.1 $119.00EPROM Burner CardAIC.1 $89.00Integer CardAEC -1 $89.0080 Column CardAZC.1 $89.00Z80A (CPM) CardAPC1 $89.00Parallel Printer CardASC.1 $89.00Serial Printer Card

ALC1 $79.0016K RAM (Language) CardAKB-2 $109.95Keyboard; Numeric key pad with function keys, replace-ment for APPLE IIAC2 $99.00Beige APPLE II Case (for above keyboard)Case & Keyboard numeric $190.00APS-2 99.00Switching Power Supply for APPLE II; +5V a 5 amps,+ 12V a 3 amps, - 5V a v. amp, - 12V a v. amp; clwon -off switch & connecting wiresAAA -2Disc Drive, 51/4", APPLE II Compatible, ExcludingController Card $299.00with controllerADC -1

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Electronic MailIs the postman hanging up hisbicycle clips for the last time?

We'll let you decide.

By Roger Allan

THE DEVELOPMENT OF new technol-ogies for high-speed transmission is alogical extension of the growth of dataprocessing evident over the last 20 or 25years. Without the necessary data trans-mission links, economies associated withlarge scale processing of data wouldgenerally not be available to relativelysmall branch offices of large corporationsand governments. The linking of evenquite large regional branches to centraliz-ed data banks or the access by small out-posts to powerful programming is mademore attractive by the development of im-proved transmission quality and volumecapability by common carrier networks.

It would be expected that expansionof computer based electronic mail wouldclosely follow, upon the establishment ofeasy to use decentralized processing andaccess systems. Mail and message func-tions should almost be a by-product of thenew technologies. While the initial im-petus is to link dispersed branches of largecorporations, once the necessary trans-mission facilities, networking and soft-ware are in place for these purposes, thenthe means for links between moredisparate organizations would also be insitu.

It has been depicted that the develop-ment of electronic mail should chronolog-ically fall into three main evolutionarystages:

characterized by the communication,primarily inter -company, of like ma-chines: fax -to -fax, communicating -typewriter -to -communicating -typewriter,Telex -to -Telex, et al;

characterized by the capability oftotally different kinds of equipment to"talk" to each other;

characterized by satellite and fibreoptic links (see "Fibre Optics", ETI, June1982) established reducing line costs.

10-DECEMBER-1983-ETI

Interfaced equipment for a variety ofcommunications and processing functionswill have proliferated. This final stagewould also be marked by serious competi-tion for control and direction of electronicmail, and for control interfaces betweenequipment to see that the entire system isused efficiently and economically as pos-sible, usually to the financial benefit ofthe government of the day.

However, the provision of softwarefor linking the many types of presently in-compatible electronic office equipmentboth within and between businesses mayprove to be a considerable obstacle to theadoption of integrated electronic mailsystems. An internationally accepted pro-tocol for communicating word pro-cessors, called Teletex, has been devised.Meanwhile, attempts are being made todevelop the first formal representation en-compassing all types of electronicsmessage systems (EMS). Besides the prob-lem of a common language, the develop-ment costs required to integrate individualoffice systems already established into ageneral electronic mail network will tendto constrain the rate of development of ageneral system.

Another problem for users of elec-tronic communications systems is theperceived lack of security of informationtransfer. To a large extent, this can beovercome by encryption of messages, al-though probably no encryption techniqueis impossible to break and it could makethe encryption of messages too expensive.Until potential users come to accept thisaspect of electronic mail, physical deliverywill continue to have an important advan-tage in this respect.

As such, the development of elec-tronic mail will be related to the extent towhich the current mail system meets userrequirements. Complaints made by postal

The major impact of electronicmail will be on business com-

munications. The facsimile unitshown is a Canadian unit from

Rapicom, Ottawa.

users in Canada, the U.S. and Australiaindicate a significant level of dissatisfac-tion, particularly among business users,with the adequacy of services, specificallyby the criteria of timeliness of delivery.

Knocking the PostiePrima facie evidence of dissatisfactionwith the speed and/or reliability of thepostal system for some business needs isthe growth of courier services. Althoughcourier services have been in existencesince the early 1930s, growth in the in-dustry has been especially strong over thelast decade. Similarly, the growth ofdocument exchange centres providing reli-able and speedy services for specializedbusiness needs is a further example ofdocument transmission outside the na-tional postal systems. The "pressure"created by commercial users for reliablealternatives to the postal system is pro-bably directly related to the existing stan-dard of service. One writer has indicatedthat both British and West Germanauthorities are less optimistic about thesuccess of an electronic mail system thancommerical systems producers because ofthe high standard of the present system.The Postfax system in Britain, for in-stance, is not thought to be widely usedbecause next day delivery is virtuallyassured for domestic users.

There is, however, little doubt thatthe major initial impact of electronic mailsystems will be on intra- and inter -business communications. in-roads can be expected in government re-lated mail and in mail received byhouseholds from business and govern-ment under future electronic mailsystems. The initial diversion of mail awayfrom the postal system is likely to be inareas which provide, at present, a signifi-cant proportion of the cross -subsidy forsery ices to remote areas and registeredpublications. This will probably place ahigher burden on those users not able todivert mail electronically, specifically thehouseholder.

Further, in the long-term, courier ser-vices are likely to face significant competi-tion from electronic systems. In a widelyquoted dramatic exmaple, 90% of onemajor U.S. courier service's income in1969 was from cancelled cheque deliver-ies. After the introduction of the FederalReserve electronic funds transfer system,this proportion had dropped to 42% by1975. While this example does notspecifically involve electronic mail, similarsuch occurrences are expected. Courierservices may benefit in the short term,however, from some services, such as fac-simile, where one "leg" of transmissionmay require rapid physical delivery from areceiving terminal or to a sending ter-minal.

From the point of view of the na-tional postal services, a critical aspect is

the extent to which developments in elec-tronic mail techniques and facilities willgenerate additional communications asopposed to diverting communicationsfrom the customary mail system. It is feltthat in the early stages such techniquescan be expected to increase the number ofcommunications, but that in the long runthere will be a substantial and permanentdiversion of communications away fromthe traditional or customary methods.

Basic TypesThere are essentially two generic types ofelectronic mail systems: facsimile and"pure" electronic.

The facsimile process is an outgrowthof British Telecom's "Bureaufax" systeminaugurated in 1980 which provided high-speed facsimile transmission to and froma large number of overseas countries (59in 1982). It was primarily designed forbusiness users. In the same year, it veryrapidly resulted in the establishment ofINTELPOST, involving the satellitetransmission of facsimile documents (viaCanada INTELSAT) between Londonand Toronto for both business and non -business users. This system has now beenexpanded to provide high-speed electronicmail links between 100 towns and cities inBritain, some dozen cities in Canada (withmore coming on stream each month, andsome cities having a number of pick upand devivery stations) and relativelysimilar numberslands, the United States, Australia, Ger-many, Argentina and Switzerland. Morecountries are expected to join shortly.

As explained by John Hovey, ServiceManager at Rapicom's Ottawa office, themanufacturer of the equipment used byCanada Post (Rapicom 3300 Desk TopDigital Facsimile Transceiver and theRapicom 6300 Digital FacsimileTransceiver), the process of transmissionis quite straightforward. The Sheet con-taining the communication is inserted intoa device which looks like a photocopier.There it is configured by being scanned bya charge coupled device (CCD), the infor-mation is processed, compressed, passedthrough a modem and transmitted at highfrequency in digitized form over groundlines. For transmission within Canada, theconnection between stations is strictly bytelephone line, though for overseastransmission the INTELSAT satellitesystem is used. When the communicationis received at the other end, it is format-ted, printed a la photocopier, put in anenvelope and consigned to the customarypost office dissemination process. Thetransmission rate is 9600 bits/second.

According to David Weinberg, Man-ager of Canada Post's Electronic Messag-ing Service in Ottawa, the cost is $5 fortwo pages, regardless of where in theworld the message is to be sent. Upon

ETI-DECEMBER-1983-11

WE'RE HERE AT LAST! NOW OPEN DIRECTLY TO THE PUBLIC

C tt H ELECTRONICS PLUS MAIL ORDER DEPARTMENT

Call 9 to 5 Mon. to Fri. - 10 to 2 p.m. Sat.

NOT ONLY DO WE HAVE MORE TO OFFER, BEING A NATIONAL WHOLESALER ACROSSCANADA, ALL OUR PRODUCTS HAVE A FULL 180 DAYS WARRANTY (UNLESS STATEDOTHERWISE). WE CARRY ONLY THE BEST QUALITY MERCHANDISE AT THE LOWEST PRICESAROUND. PLUS FREE DELIVERY ANYWHERE IN CANADA! (NO MORE PARKINGHEADACHES OR FRUSTRATING LINE UPS) ON ORDERS OF $300.00 OR MORE.

NO FANCY OR EXPENSIVE DISPLAYS JUST GOOD PRICES & EXCELLENT SERVICE

COMPUTERS

SOURCE 9000*Well built 48K compatible (to you

know what!), numeric keypad, ABSCase, heavy duty power supply, 8 expan-sion slots, U/L case $595.00

(REG. $699.00)

SOURCE 6400*The only hassle free -with APPLE -

computer. Multi -System 64K memoryboard, 9 expansion slots andunrestricted memory. No ROM and fix-able language. Therefore allowing userto create/operate any language withover 50 different expansion cards on themarket.

`Includes numeric keypad, heavy dutypower supply, U/L case, 25 functionkeys, card to run APPLEtm and more!

*No legal worries with APPLE on thisone! $795.00

(REG $849.00)

SOURCE 2000`The ultimate computer with both

6502 and Z-80 CPU's, 64K expandable to294K, built in disc printer interface, 40/80column selectable, U/L case, 25 functionkeys, numeric keypad, heavy duty swit-ching power supply LED reminder onboard and (2) volume controlledspeakers $995.00

(REG. $1149.00)`Surfboard beware*

Apple Ile "Starter System"`Inclues 64K, 80 column card,

drive/controller, Apple Ill monitor andstand $2495.00

(REG. $2795.00)

'**COMING SOON IBM CLONES **Source Cards16K $65.00Z-80 $65.0080 column $79.00Disc Controller $65.00Freeze Play $99.00(Wildcard emulator/disk/documenta-tions)192K Disk RAM $499.00(Virtual Disc Card with (2) software pkgs)Grappler/printer $79.00Soft switches $29.00(for 80 col. card)

Perisoft CardsMessenger(Dual/ink RS232C,year warranty)Timelink(Built-in firmware,warranty)

$119.00built in firmware, 1

$109.00alarm clock, 1 year

Wizard Cards16K $109.0080 column $229.00IPI Printer $95.0016K Buffer card $199.00(Above all 2yr warranty)

ACCESSORIESFlip 'n File (Holds 50 diskettes) $32.00(Holds 50 diskettes)Hayes Joysticks $59.00Pride Joysticks (self centering) $40.00Apple Stands (Fits 2 drives/monitors) $39.00Printer Stands $35.00(5" high, paper feed slot)Muffin Fans (dual outlets) $50.00Siemens Fans $95.00(Surge supression/f ilter/outlets)Paper $39.00(2100 sheets, 9'/:x11 perforated)Printer Ribbons SCALLRibbon Re -Inking (Saves on new ribbons) SCALLPlott II Graphics Table $129.00Light Pen/Interf ace/Sf twr $369.00Hayes Modems SCALL

DISKETTESGenerics $23.00BASF $29.00Dysan $33.00

All box in 10's & SS, DD

Send us any diskettes and a list of particular soft -wares you want & for $10.00 ea. we will have it mailedto you. (Providing its on our list)($25.00 CLUB REGISTRATION FEE)

PERIPHERALSCUMANA "Rainbow I" Disc Drive 5319.00

'Siemens drive, direct from U.K., (REG $339.00)If you thought Quentin was good try this drive!

CUMANA "Rainbow II" Disc Drive 5379.00'IBM, D.D. Drive, Siemens based.

Slimline Drives $319.00

Zenith green screen monitors $129.00NOTE: Call for quotes on hard disc drives, ambermonitors or whatever you can't find.

C-ITOHPRINTERS

Prowriter I (Parallel) $599.00Prowriter II (Parallel) $1009.00Starwriter F-10 (40 cps letter quality) $1775.00F-10 Tractor option $399.00

OKI-DATA 160 cps PrintersMicroline 92 $799.00(U.S. hottest printer, prints 160 cps dot matrix, 40 cpsletter quality)Microline 93 (15" Carriage) $1599.00Microline 82A $669.00Microline 83A (15" Carriage) $999.00Microline 84P (200 cps) $1599.00Microline 84S (200 cps) $1659.00

EPSONFX-100 $979.00FX-80 $879.00FX-80 FT $699.00NEC 8023A $699.00Toshiba P1350 $2279.00(Top of the line)

Introducing: The RIteman Printer Epson FX-80 emulator, 120 cps, 9x9 dot matrix,

true 1:1 dot ratio, bl-directional, slimline $599.00

SMITH CORONA SPECIAL $579.00TP-1, letter qualitySMITH CORONA $750.00TP-2 New Model, letter quality

*IF YOU DON'T 'SEE IT! ASK!*MAIL ORDERS: Send certified cheque/money order. Ontario residents mustadd 7% PST Visa card accepted: cardno., name, signature, exp. date and bankname please!

C & H ELECTRONICS PLUS23 Passmore Ave., Unit 11, Scarborough, Ontario. M1V 2J8.

(Just (1) light North of Finch right side of Kennedy Rd.)(416)292.0813 - TELEX 065-25320 C&H TOR


ATTENTION: Clubs, schools, and co-op pur-chasers call for our special pricing catalogues.

Dealer inquires welcomed!Contact: Rob Laver

Electronic Mail

receipt, the envelope can be sent throughthe regular mails at no additional cost, orsent special delivery ($1.06 extra inCanada, $5 in Germany, for instance).Further, the recipient can be telephonedupon receipt of the message, and can stopat the post office and pick it up. Theoreti-cally, a message can be sent from Torontoto, say, Calgary and picked up at that enda mere few minutes after its receipt. It issupposed to be very good for typewrittenmatter and drawings, though it does nothave the capability of colour.

Way of the Future?According to Weinberg, "handwrittenmail is on the way out," and electronicmail "is the way of the future. UnlessCanada Post jumped into electronic mail,we would be left behind." Today, IN-TELPOST has not been pushed byCanada Post, but there is a large publicitycampaign planned for the fall and springof 83/84. Details as to the volume gener-ated over the past three years was notavailable, though a spokesperson forCanada Post has said, "it's not much."

The two countries which have heavilyinvested in electronic mail via the nationalpostal system (as opposed to private car-riers or the adjuncts to various telephonecompanies) are Britain and the UnitedStates.

In Britain, the system is known asTelecom Gold, in which a laser beam op-tically reads the printed document andthen transmits it to any one of severalthousand electronic mail boxes, or viceversa. Further, the system links into inter-

national services so that documents can betransmitted to micro -computer usersworldwide. Should the recipient not havea microcomputer, the mail is sent fromthe nearest receiving station by traditionalmethods for the last leg of its transmissionjourney.

It is, however, the U.S. Post Office'sE-COM system which seems to be the cur-rent state of the art in this area.

As explained by E.M. Alexander ofthe RCA Corporation which provided theequipment for E-COM to the USPO,"INTELPOST is not the bellwether forfuture electronic mail systems," thoughE-COM is. The difficulty lies in the quali-ty of the finished product; INTELPOST,being a facsimile reproduction system,isn't really very good, while E-COM usesgood quality dot-matrix printers (number-ing from 3 to 9, depending on the receiv-ing station of which there are currently 25)on good quality bond paper and providesa quality which is superior and far morebusiness -like than INTELPOST's finishedproduct. Further, facsimile transmissionrequires the company to either possess apiece of special equipment into which thedocument can be fed, or to physically takeit to the nearest USPO which would havesuch a device (similarly in Canada). WithE-COM, on only needs a modem, and amember of staff who has received a fewhours training and a practice session.

RCA first became interested in thesubject and commenced research on howto do it some seven years before the USPOawarded them a $38.1 million dollar con-tract to provide the hardware, a training

station and set-up help. The systemdeveloped is dependent on land lines usingcommon carriers, due to FCC regulations.It is TTY synchronous, operating at 300or 1200 baud rates, with 2400 baud (andup) rates available with additional equip-ment. When received by any one of the 25offices currently available in the U.S., thecomputer, on-line twenty-four hours aday, automatically tapes the message atthe front end by a dumb processor. Themessage is then automatically transmittedto the nearest available station to the reci-pient, where it is re -processed, elec-tronically sorted, the message typed out(on 80 -character lines at 600 lines perminute), automatically sorted, placed inthe envelope which is typed, and senteither through the regular mail system orby special delivery. The modus operandiof the computer transmission follows theASCII guidelines, specifically an eight bit,alphanumeric system providing upper andlower case. As such, a message, in adistinct envelope, can be received any-where in the contiguous United Stateswithin two days.

The E-COM system will acceptmessages in three different formats:

Single Address Messages (SAM)which are those in which a unique text ac-companies each address;

Common Text Messages (COT)which are those in which a common text isaccompanied by a list of addresses (eg. forbulk mailings);

Text Insertion Message (TIM) whichare those in which a common text is ac-companied by both a list of addresses and


Electronic Mail

BCDDATA

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Exampks of the reproduction quality of the electronic mail service. Agood quality typewriter (a) produced the best copy, along with originalline drawings (b). Photocopies (c) were somewhat fuzzy, and originalphotographs were not usable at all.

a unique text to be inserted in each printed message.To date, the use of this system is running at about 1 million

messages a month.

Small Business UsersAt a cost of 31C (US) per page, and an additional 9C for subse-quent pages, the price is comparable with regular mailing services.There are, however, two problems with the system. One is that asender must send a minimum of 200 items per transmission,though this may be one item to 200 addresses. For smallbusinesses this can be a problem, though there are intermediarycompanies which stand between the USPO and the user who willcollect messages in less than 200 and "batch lot" them for an ad-ditional fee. Secondly, very small businesses who have not as yetpurchased or leased a microcomputer for the initial compositionof the message must likewise use an intermediary organization foran additional fee.

Without a great deal of publicity, and recognizing that thereare a few wrinkles in the system to be worked out or adjusted,such as permitting smaller batch lots to bring more smallbusinesses into using it, the provision for a business reply orcourtesy card reply, et al, the system has nonetheless grownquickly. Further, according to Alexander, the USPO has "notreceived so much as a single complaint from a user." The ex-pected volume of transmissions for this system is 1.1 billion piecesper year by 1986.

And as for the postman about to hang up his bicycle clips?Well, there will always be little towns and hamlets left to service.

INTELPOST permitted ETI to partake in a demonstration of thefacsimile electronic mail system. The art department kindly madeup a specimen melange of bits and pieces, which this author thenphysically took down to the Canada Post Office on Front Street,Toronto. First problem was that the pictures and diagrams weremounted on thin card. This didn't fit the machine, so with thehelp of a staffer and a pair of scissors we transferred the items to apiece of paper. The paper didn't fit the machine, being too wide.Further use of scissors. Finally it worked.

The item was transmitted at 10:30 Toronto time on a Friday,and was collected from the mail box by Our Man In Calgary, Mr.B.J. McLauren, at five -thirty the same day. He immediately con-signed it to the mails to be returned to us; it arrived on Mondaymorning.

helpyour

Heart Fundhelp your

heart


Which Battery To Use? Ill

MANY PEOPLE HAVE a tendency toreplace conventional 'dry' cells with therechargeable nickel -cadmium type simplyto avoid replacement costs, but this prac-tice may not be cost effective and can evenlead to reduced equipment performanceand greater cost. In order to make someform of meaningful comparison betweentypes, it was necessary to select one com-mon size of cell and look at the perfor-mance under similar load conditions.Also, because the performance of carbon -zinc cells is more dependent on usage thanalkaline or NiCad cells, a definite state-ment as to which is best, cannot readily bemade.

The purpose of this article is to try topresent a guide to the selection of cell typebest suited for an application, bearing inmind equipment performance, duty cycle,current demand, weight and cost. The in-formation presented here has been obtain-ed from the data sheets of many manufac-

turers and should not be regarded astypical of any particular make. Because ofthe variation in performance of carbon -zinc cells with differing loads, the presen-tation has been optimized to give areasonable overall guide to performancewithout being too optimistic.

Cells TestedThe basic cells compared are the nickel-cadmium rechargeable type, the ordinarycarbon -zinc dry cell, both normal andheavy duty (leclanche type), and themanganese dioxide -alkaline type. The sizeof the cells selected for comparison are the'AA' or UM -3, SAA designation R6. Inthe case of the NiCad, this is a 450 mAhour capacity cell. The load characteristicselected was a current drain of 30 mA forfour hours per day. This is typical ofmuch portable equipment such as walkie-talkies, portable radios, calculators, etc.This was also the load which was easiest to

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compare on a range of data for variouscells.Result of ComparisonsGenerally, the comparison here showsalkaline cells to have a performance abouttwice that of ordinary carbon -zinc cells;however, they can be many times better,depending on usage. Alkaline cells havehigher efficiency when used for con-tinuous or heavy load (high current) ap-plications where the conventional carbon -zinc cell is less effective. The rechargeableNiCad is good for heavy current applica-tions, provided the correct supply voltagecan be achieved. Unfortunately, carbon -zinc and alkaline cells are not directly in-terchangeable with NiCad cells due to dif-fering terminal voltages. This is caused bythe different types of materials and con-struction used for these cells. The result isthat while carbon -zinc and alkaline cellshave a terminal voltage of 1.5 V, theNiCad cell has a voltage of only 1.2 V.

ET1-DECEMBER-1983-15

Which Battery to Use

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THE CROSS ON EACH LINE INDICATESTHE APPROXIMATE POINT AT WHICH EACHTYPE OF CELL IS NORMALLY CONSIDEREDFULLY DISCHARGED OR 'FLAT'.

TIME (HOURS)so

Fig. 1. The discharge performance of various cells. The discharge characteristics of a lead -acid cell areshown for comparison. Note that terminal voltage cannot be used to indicate the state of charge ofNiCad cells.

Figure 1 shows the performance ofthe various cells and that of a similarcapacity lead -acid cell for comparison. Itis important to note that the terminalvoltage cannot be used to indicate thestate of charge of the NiCad cell, but canbe used as an approximate indicator for`dry' cells. NiCad cells are about 25% to30% heavier than 'dry' cells and becausemore of them may be required for thesame voltage, this could mean a substan-tial weight penalty in portable equipment.

Batteries At WorkThe place where these various cells mustwork is in the equipment, and this iswhere many factors become important.The points to be considered are: duty cy-cle - is the load to be continuous or inter-mittent high current, or is it to be low cur-rent, continuous or intermittent? Operat-ing environment - will the power be re-quired at extremes of temperature? Whatis the design voltage of the equipment andcan sufficient cells be accommodated toprovide this? Replacement or recharging- in a particular situation one optionmay be preferable to the other, and whichoption is cost effective? Operational life- how long will the selected cell operatebefore recharge or replacement isnecessary? Shelf or storage life - howgood is a particular cell after a period ofno use?Duty CycleThis will have a major effect on the per-formance of cell in any situation. Con-ventional carbon -zinc cells perform bestat a relatively light load when operated in-

termittently. This allows a degree of re-covery between periods of use. The servicelife of alkaline cells is relatively constantregardless of whether use is continuous orintermittent. This type of cell then showsits advantage mainly when continuous useis required. It can have a service life ofthree to ten times that of carbon -zinc cellsin ideal circumstances.

Another advantage of the alkalinecell is its ability to supply considerablyhigher currents than the carbon -zinc type.In fact, the current available from alkalinecells can approach that from NiCad re-chargeable cells in some circumstances.For high current loads, intermittent orcontinuous, the NiCad cell may be prefer-red, either because other cell types cannotsupply the required current or becausedischarge is so rapid that continualreplacement would be necessary. Substitu-tion of carbon -zinc or alkaline cells withNiCads should only be undertaken afterconsideration of all the factors involved,including operating environment, equip-ment voltage requirements and storagelife.

Operating EnvironmentCarbon -zinc cells deteriorate quickly attemperatures above about 50°C andbecome rapidly unable to deliver usefulcurrent below -18 °C. Alkaline cells showbetter operating characteristics at ex-tremes of temperature. Although it is dif-ficult to determine the upper temperaturelimit of these cells, it is considerably betterthan carbon -zinc cells. Alkaline cells per-form reasonably well down to tempera-tures of -40°C.

NiCad rechargeable cells have anoperating temperature range of about-20 °C to + 45 °C but should not be expos-ed to temperatures below 0°C whilecharging. Generally, their operatingtemperatures are about the same as forcarbon -zinc cells. There may be sometempterature rise in NiCad cells duringcharging or heavy discharge, and this fac-tor should be considered if these cells areused as a replacement for 'dry' cells insensitive or critical equipment.

Design Voltage of EquipmentThis is an important factor when con-sideration is being given to replacingcarbon -zinc or alkaline cells withrechargeable NiCad types or replacingNiCads with `dry' cells. In equipmentsuch as portable transceivers, satisfactoryoperation depends greatly on the availablesupply voltage. Some of this equipment isdesigned to operate from NiCad cellswhile the other is intended to use 'dry'cells. Most such equipment has a specifiedoperating range of voltages and attempteduse outside of this range will result inseverely degraded performance, no opera-tion at all, or possible damage to theequipment. Typical ranges for nominal 12V equipment are 11 V to 14 V or 10 V to15 V. There is a temptation to replacecarbon -zinc or alkaline cells with an equalnumber of rechargeable NiCad cells butbecause of the difference in terminalvoltage (1.5 V as compared to 1.2 V) a ful-ly charged NiCad battery may not meetthe minimum voltage requirements ofequipment.

Figure 2 shows the performance ofvarious battery types in a piece of 12 Vrated equipment such as a portabletransceiver. Note that if provision is onlymade for eight cells, then replacementwith lower voltage types can result in in-sufficient supply for the correct operationof the equipment. Often the mere fact thatthe equipment operates at all under theseconditions is more a tribute to thedesigner than the performance of thepower source! On the other hand, replace-ment of NiCad cells with 'dry' cells couldallow the equipment voltage specificationto be exceeded.Replacement or RechargingWhich is best here will depend very muchon the user requirement. For example, atransceiver used by emergency servicesmight be more quickly restored to serviceby replacement of batteries than byrecharging. For personal use, wherefailure due to battery discharge is not socritical, recharging may be acceptable. Ifthe equipment is in heavy or continuoususe, then recharging may be a viable alter-native to replacement.

The cost of any option will depend onhow often replacement is required, the


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Which Battery to Use

15.0

145

14.0

13.5

13.0

12.5

VOLTS12.0

11.5

11.0

10.5

10.0

9.5

9.0

10 NICAD CELLS

8 ALKALINE CELLS

l88a NORMALDRY CELLS

8a ZAD 7ELLS-7 AR-

a HEAVY DUTYDRY CELLS

TIME (HOURS)30

NORMALEQUIPMENTOPERATINGRANGE14V- 11V

EQUIPMENT OPERATION IS DEGRADED IN THIS RANGEAND TRANSMITTER POWER OUTPUT IS REDUCED TOBETWEEN 50% AND 20% OF NORMAL.

()POTATION ItaHIS AREA IS POORTO MARGINAL WITH SOME EQUIPMENT NOTOPERATING AT ALL. ANY OPERATION OF12 V RATED EQUIPMENT CAN ONLY BEREGARDED AS UNRELIABLE AT BEST.

40 50

Fig. 2. The performance of various battery types in a 12 V operated handheld transceiver. Note thayou cannot expect to replace eight dry cells with eight NiCads.

100

% eo

70

so

50

0

ALKALINE

STANDARD CARBON -ZINC DRY CELL

LEAD -ACID (CAR BATTERY)

LOW DISCHARGE RATE CELL

NICAD RANGE

HIGH DISCHARGERATE CELL

1 2 3 81

WEEKS2

MONTHS4 5 6

Fig. 3. All secondary cells self -discharge, which gives them a certain 'shelf life'. Here, the self -discharge characteristics of the various cells are shown. A lead -acid cell is included for comparison.

higher initial cost of rechargeable cells,(and you may need more of them), thecost of a charger and the cost of an addi-tional battery pack if operation is neededwhile recharging is in progress. Anotherimportant factor, especially in anemergency environment, is the availabilityof power for recharging. If such a sourceis not readily accessible, a user may be ill-advised to use rechargeable batteries atall.

Operational LifeThe effective operational life of a batterymay become very important if access to

replacement or recharged cells is difficult.As can be seen from Figure 2, the NiCadcells under this load will supply power forabout 15 hours of operation. This is con-ditional on the battery being fully chargedand in good condition. Ordinary carbon -zinc cells will provide about the same ser-vice life and heavy duty ones about twicethis. Alkaline cells can be expected to havea greater operating life, about three timesor better, than either NiCads or carbon -zinc as compared here.

There is a further factor whichshould be considered where the use ofNiCad cells is contemplated. It has

become recognized that NiCad cells tendto develop a 'memory' of their usage pat-tern. What appears to happen is that if acell is used to, say, only 50% of capacityand then recharged, after a few cycles ofthis pattern, the cell then becomes onlycapable of delivering 50% of rated capaci-ty before going 'flat'. This condition canbe reversed by correctly cycling the cellthrough several discharge and chargecycles, but unless this condition isrecognized as developing, it may seriouslydegrade the operational life of the equip-ment in which it is used.Shelf Life or Self DischargeAll cells will discharge by themselves whennot in use, to a greater or lesser degree.This self discharge will determine thelength of time for which a cell can be leftunused and still be able to deliver areasonable proportion of its originalcharge. The major factors which influencethe rate of self discharge are storagetemperature, amount of charge at storage,and the condition of the cell.

The definition of shelf life issomewhat variable, but for carbon -zincand alkaline cells appears to be the timetaken to decrease to 90% of initial capaci-ty. Accepting this definition then, givesthe following approximate storage life-times for cells in good condition.

Carbon -zinc cell 8 to 9 monthsAlkaline cell Over 2 yearsNiCad cell 3 days to 4 weeks

These storage times are based on aconstant temperature of about 20°C to25 °C. Storage life may be improved bystoring the cells at 5-10°C. Generally,higher temperatures cause more rapiddegradation. Storage life is also shown ingraphical form in Figure 3. An approx-imation for a lead -acid car battery typecell is shown for comparison. NiCad cellsappear to show up poorly in this regardand some manufacturers now claim tohave substantially improved thischaracteristic. The self discharge ofNiCad cells depends on the type of cell,whether it is intended for high or normalcurrent discharge. The condition of thecell is also important, whether it has beencycled correctly, the age (number ofcycles), the environment in which it hasbeen used and the state of charge atstorage.

Consideration of the information pro-vided here may be able to assist you tomake a better informed decision as to thebest power source for your battery oper-ated equipment. It is not practical to coverall the eventualities and applications in ashort article, but at least this should pro-vide some guide to the cost effectivenessand practicability of the battery that youselect. Most manufacturers will providedesign and engineering data on requestshould you need to make a more detailedanalysis of your particular needs. an


contents of the magazine'

At the time of going to press, the articles mentioned are in an advanced stage of preparation.However, circumstances

may result I:changes to ;h.:::With 1984 approaching, you'd expect your appliances to beMicros in Appliances

:;A::..km..:,.,Ak.:..

::::::;-.:-,:-s-::::per,m,v

listening in to your every word. Eric McMillan looks at thecurrent state of the art and proves that you have nothing toworry about ... yet.

Travelling Wave Tube AmplifiersRoger Allan continues his high-tech inquisition with a look atTravelling Wave Tube Amplifiers. Find out why travellingwave tubes need to be amplified.

PLUS!Accurate Risetime Measurements!

Hearing Aid Induction Loops!Pop Amps!

LM396 10 Amp Regulator!

Para -QThe Para-Q (short for Paraquat) parametric equalizer isdesigned to take the funny stuff out of whatever signals youput through it.

NiCad Charger/RegeneratorTo accompany our bat-

tery article, here is aNiCad charger which ex-

tends battery life myminimizing "memory"and metallic deposits.

by Mike Punnett

NICKEL -CADMIUM BATTERIES(NiCads) are becoming increasinglypopular as replacements for conventionaldry batteries in a wide range of equip-ment. Properly used, they can give anenormous cost saving over the life of theequipment, but if misused, tend to failearly.

Since NiCads have a tendency to self -discharge over a few months, they have tobe charged regularly. Furthermore, toavoid the inconvenience of a flat battery,they are often "topped up" with chargeeven when far from discharged. This leadsto an effect known as whiskering, wherefine deposits of cadmium build up, whichcan partially short-circuit the cell, as wellas reducing the active electrode size. Thisleads to a loss of capacity; a 500rnAh cellmay be reduced to 300mAh after a year oflight service and frequent charges.

It has been found that "cycling"NiCads can return them to an almost -newcondition. This process involves discharg-ing the battery hard (at the 1 hour rate,e.g. 500mA for a 500mAh battery), until itreaches the minimum safe voltage -NiCads can be easily damaged by over -discharging. A full charge at the 10 hourrate follows. This rather rough treatmentdisintegrates the whiskers of cadmium,

and the full charge redeposits the metal onthe electrodes. However, cycling NiCads"by hand" is a risky business, since theycan easily be damaged.

The ETI NiCaddy was designed tocycle NiCads correctly and easily. It uses aminimum of components, and has two"programs": cycle and charge. Operatingthe unit is very straightforward: the Nic-Cad is connected to it, and the ap-propriate button for the required programpressed. Cycle mode discharges the bat-tery to its minimum safe voltage, and thenswitches to charge mode, in which the unitfunctions as a constant -current charger,automatically turning off when the bat-tery reaches full charge. If the NiCad isalready below its minimum safe voltagewhen connected up, the unit willautomatically enter charge mode, over-riding the switches, which are re -enabledwhen the battery rises above minimumsafe voltage.

ConstructionConstruction of the unit is quitestraightforward, either on the PCB orstripboard. Sockets are recommended forthe ICs particularly IC2 which is a CMOSdevice. Do not forget the three wire linkson the PCB.

115VAC

E 0

SWIFS1

RV110k

'LOW'

RI2k2

Cl +1000u ''

40V C2 +100u25VT 220nT

01

VREF

PIN 3 ICIPIN 14 IC2

10

02

C4T 220nCC

RV2105

'HIGH'

11

'Cl.

IC1b

R210k

13

R310k

2

LED1'DRAIN'

R4152

4IC2. IC2b

DI

ZD2R6 (SEE riE10k TABLE)

6

5 P61'CYCLE'

1-)---VF17

PIN 12 IC1PIN 7 IC2

1311 10

12 IC2c IC2d

2k2

R89 252

R5 1k2 LED2

PB2'CHARGE'

R10(SEE

TABLE)

04

NOTE:ICI IS LM339IC2 IS 401101 IS 2N3904Q2 IS TIP31A03 IS 2N290504 IS 2N3053D1 IS 1N4148ZD1 IS 18V ZENERZD2 IS ZENER (SEE TABLEFOR VOLTAGE)LED 1,2 ARE any LEDBR1 IS ZA BRIDGE

R9(SEETABLE)

NICAD, BATTERY

CHARGE


Table 1 gives component values forAA size (500mAh) cells (see later fordetails of use with other battery sizes).The circuit will work with batteries of upto eight cells. Remember that R11 will gethot, since the battery is dischargedthrough this. For power ratings over 4 W,this component should be mounted offthe board, preferably outside the box, toaid heat dissipation. Some of the tran-sistors are fitted with heatsinks; Q1 has analuminum heatsink (see overlay), Q3 andQ4 have push -fit TO5 heatsinks.

Testing and CalibrationCheck the voltages across C3 and C4.Both should be in the range 16.5-17.4 V.If not, the power supply section should beinvestigated. The precise values do notmatter, since the calibration will allow forsome variability.

If the power supply is working pro-perly, the unit can be calibrated. RV1 isset to the minimum safe voltage for thebattery; this is 1.1 V per cell (i.e., 4.4. Vfor a four cell battery). An accurate, highresistance voltmeter connected to pin 8 ofICI will enable the voltage to be checked.RV2 (full charge voltage) must be setrather more accurately, since the step involtage which a NiCad exhibits as itreaches full charge is quite small. The bestmethod is to set the voltage too high atfirst; about 1.7 V per cell on ICI pin 11 is

adequate. The operation of the unit isthen checked with a battery which isknown to be in full working order; at thisstage the circuit should perform asdescribed above, except that it will notturn off after charging. The charging cur-rent can be checked; it should be 0.1 ofthe cell capacity (i.e., about 50mA for500mAh (AA) bateries). The test batteryis then left on charge for a long period -20 hours if flat. This guarantees that itstabilizes at full charge voltage. Since thecharging is constant -current, there is no

risk of damaging the battery by chargingfor too long. At this point, RV2 can beslowly turned down until the circuit justswitches off, and the setting re -checked.The unit is now completed.

No ofcells

Table 1D3 volt-age V

R9 R10ohms/wattsohms/watts

2 10 210/1 4.7/24 8.2 160/0.5 10/46 5.1 100/0.5 13/78 3.6 68/0.25 18/10

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NiCad Charger/Regenerator

ModificationsThe circuit was originally designed for AAsize (500mAh) NiCads, since these are themost widely used, but it can easily beadapted for other sizes by changing R9and RIO. These are calculated from thequoted values simply by reducing theresistance and increasing the wattage inproportion to the capacity; so for a 1 Ahsix -cell battery, R9 would be 50R 1W andRIO, 6R 15W. (The values do not have tobe absolutely exact, of course). For cells

over 1 Ah capacity, it is best to uprate Q3and Q4; since the circuit will be on forlong periods, it is advisable to rate com-ponents generously, especially heatsinks.Replacing Q3/Q4 with TIP32/TIP31respectively, mounted off the PCB on asuitable heatsink, will enable the unit tocope with cells up to about 4 Ah. As arough guide, allow 1 Watt dissipation perAh cell capacity when choosing heatsinks.Remember that the heatsink on Q1 mayneed uprating also. Allow a dissipation of1.2 W per AH cell capacity.

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The power supply section is quitestraightforward, using a very simple voltageregulator. Vcc is not critical, but thereference voltage, Vref, must be stable, eventhough the precise voltage is not important.With a separate regulating transistor (Q1)the circuit shown is quite adequate. The tworeference levels (the points at whichdischarge and charge respectively ter-minate) are derived by RV1 and RV2.

ICI is a dual comparator which has anumber of advantages over similar units,including single -rail operation, the abilityto accept inputs at near -ground potential,very low offset, and open -collector outputs.In the circuit, the output of ICI a goes lowto indicate that the battery has reachedminimum voltage, and that of 1C1b goeslow when maximum voltage is reached.

IC2 is wired as two flip-flops, one fordischarging (IC2a,b) and one for charging(IC2c,d). Pressing "Cycle" sets thedicharge flip-flop and clears the charge flip-flop (via D2). When the battery reachesminimum voltage, or "Charge" is pressed,the discharge flip-flop is cleared and thecharge flip-flop is set. The battery reachingfull charge clears the charge flip-flop butdoes not set the discharge flip-flop. Thestatus LEDs are driven directly by the twoflip-flops, which also drive the outputstage. The latter consists of a discharge cir-cuit - when Q4 is turned on, the batterydicharges through R11 - and a constantcurrent circuit consisting of Q3 and its an-cilliary components, which is turned on byan active -low signal (when IC2 pin 11 is

high, Q3 is driven fully off and passes nocurrent).

Resistors (all 1/4W 5% unless stated)R1,7,8 2k2R2,3,6 10kR4,5 1k2R9,10 See textRV1,2 10k multi -turn

preset potCapacitorsCl 1000u 40V PCB mounting

electrolyticC2 100u 25V PCB mounting elec-

trolyticC3,4 220n polyesterSemiconductorsICI LM339IC2 401IBQ1Q2

Q3Q4DID2D3LED1,2BR1

2N3904TIP31A2N2905 (but see text)2N3053 (but see text)18V 400mW Zener1N4148 or similar400mW Zener (see Table 1)Any 0.125" LED2A bridge rectifier

MiscellaneousPB1,2 Min push -to -make switchesSW1 Two -pole power switchFS1 lA power fuse and holderT1 Power transformer, 15V lA

secondary (but see text)Two 14 -pin DIL sockets, case to suit, bat-tery connectors, heatsinks as required (seetext).



Expanded Scale VoltmeterCoverin The 10-15 V RangeA simple, low-cost instru-ment that can be built intopower supplies or used as aportable or fixed 'battery

condition' monitoringmeter.

COMMON STORAGE batteries to powernominal 12 V DC electrical systems have aterminal voltage that ranges from a littleover 10 volts when discharged to around15 volts when fully charged, the operatingvoltage being somewhere in the range 11.5V to 13.8 V. Lead -acid batteries, for ex-ample, may have a terminal voltage underrated discharge that commences at around14.2 V and drops to about 11.8 V. A 12 V(nominal) nickel -cadmium battery maytypically have a terminal voltage underrated discharge that starts at 13 volts,dropping to 11 volts when discharged.

Equipment designed to operate froma nominal 12 V DC supply may onlydeliver its specified performance at a sup-ply voltage of 13.8 V - mobile CB andamateur transceivers being a case in point.Other DC operated equipment may per-form properly at 12.5 V but 'complain'when the supply reaches 14.5 V.

To monitor the state of charge/dis-charge of a battery, a battery -operatedsystem or the output of power supplies,chargers, etc., a voltmeter which can beeasily read to 100 mV over the range of in-terest, i.e., 10 to 15 volts, is an invaluableasset. This project does just that.

This instrument, being of the trueanalogue type, is intended for exactingmeasurement and is better characterizedas a test instrument.

The CircuitAn LM723 variable voltage regulator IC isemployed to set an accurate 'offset'voltage of 5 V, and the meter (M1) plusthe trimpot RV2 and R3 make up a 5 Vmeter, with the trimpot allowing calibra-tion. The negative terminal of the meter isconnected to the output of the 723 so thatit is always held at 5 V 'above' the circuitnegative line. The positive end of themeter goes to a zener which will not con-duct until more than 5 V appears betweenthe circuit + ye and -ve lines. Thus themeter will not have forward current flow-ing through it until the voltage betweenthe circuit + ye and -ye rails is greater than

10 V, and will read full scale when itreaches 15 V (after RV2 is set correctly).

The meter scale limits may be ad-justed by setting the output of the 723higher or lower (adjusted by RV1) and set-ting RV2 so that the meter has an increas-ed or decreased full-scale deflectionrange.

A variety of meter makes and sizesmay be used.

ConstructionMechanical construction of this projecthas been arranged so that the pc boardcan be accommodated on the rear of anyof the commonly available moving coilmeter movements. We chose a meter witha 55 mm wide scale (overall panel width,82 mm). A meter movement with a largescale is an advantage as it is considerablyeasier, and more accurate, to read thanmeters with a smaller scale. It also pays tobuy a 2% fsd accuracy meter for best ac-curacy.

Having chosen your meter, drill outthe pc board to suit the meter terminal

HOW IT WORKSThe meter, Ml, is a 1 mA meter with seriesresistance - made up of R3 and RV2 - sothat it becomes a 0-5 V voltmeter. Thenegative end of the meter is maintained at 5V above the circuit negative line by the out-put of ICI, a 723 adjustable regulator. Thepositive end of the meter is connected to thecircuit positive line via ZD1, a 4V7 zenerdiode. Thus, no 'forward' current will flowin the meter until the voltage between thecircuit negative line and the circuit positiveline is greater than 5 + 4.7 = 9.7 volts.

Bias current for the zener is providedby a FET, Q1, connected as a constant cur-rent source so that the zener current is ac-curately maintained over the range of cir-cuit input voltage. This ensures the zenervoltage remains essentially constant so thatmeter reading accuracy is maintained.

The trimpot RV1 sets the outputvoltage of the 723. This determines thelower scale voltage. Trimpot RV2 sets themeter scale range. More resistance increasesthe scale range, less resistance decreases it.

Diode DI protects the circuit againstdamage from reverse connection.

spacing first. The components may thenbe assembled to the board in any par-ticular order that suites you. Watch theorientation of the 723, ZD1, the FET andparticularly DI. The latter is an 'idiotdiode'. That is, if you have a lapse of con-centration or forethought and connectyour project backwards across a battery,the fuse will blow and not the project.Fuses are generally found to be cheaperthan this project!

Seat all the components right downon the pc board as the board may be posi-tioned on the rear of the meter with the

7.1 V

12.0 V

0FS1

65011mA

RV110k

2.3 V

ICILM7231:21

7.1 V

VOLTAPES WITH DIMAND 12 VOLTS INAND UNIT CALIBRATEDTOTAL CURRENT DRAIN 12.5 mAMETER READS BACKWARDSBELOW 10 VOLTS

01M13019

DlIN4001

10-15 V PI


Expanded Scale Voltmeter

M1- ye

+ve

TAG

5

TOP

10-15 Vdc

4u71

C1 + 1)

R2

4=3 390R RV110kC2

SET LOWER

-ve

100n

BOTTOM2N3819

M1+ve

Capacitors

tantalum

BANDI 1-

DIODE

components facing the meter The size ofC2 may give you a little trouble. We useda `Monobloc' type capacitor - as com-monly used on computer pc boards asbypasses. Alternatively, a 100n tantalumcapacitor ( + ye to pin 2 of ICI) may be us-ed. The actual value or type of capacitor isnot all that critical.

We have used multiturn trimpots forRV1 and RV2 as they make the setting upa whole lot easier.

Resistors (All 1/2W Ph or 207o metal film)RI 470RR2 390RR3 lkRV1,RV2 10k cermet multiturn horizon-

tal trimpot

CapacitorsCl 4u7/10 V tant.C2 100n ceramicC3 10u/10 V tant.

SemiconductorsICIZDIQIDI

LM723CH4V7, 400 mW or 1W zener2N38191N4002 or similar

MiscellaneousMI 1 mA meter (see text)FS1 500 mA fuse and in -line fuse

holderpc board; meterscale to suit meter.

MEMORY SPECIAL4116 150nS MOT $1.994116 200nS NEC $1.754864 64K x 1 Hitachi 200NS $7.992708 1 Kx8 $5.552716 2Kx8 Hitachi,NEC $4.502732 4Kx8 NEC $6.992764 8K x 8 Mitsubishi . . . . $10.506532 $7.502532 $7.652114 200nS (Hitachi) $1.752128-2 $7.99

Japanese Parts SpecialistsPARTS 100% GUARANTEED

CPUZ80 $5.99Z80A NEC $6.756502A 2M Hz $6.996502 $6.506845 CRT Controll-er (Hitachi) $8.996522 $6.998088 $24.50

4164 64K x 1 OKI 150 NS $ 8.252114 300 NS Hitachi $ 1.752016 150 NS $ 8.256116 150 NS $ 8.7527128 $37.95Call for quantity price.OEM Enquiries Invited.

Peripherals8748D N EC .$24.508741 NEC . $32.508251 NEC .. $5.998253-5 NEC . $9.008257-5 NEC . $9.25

TTLLS323LSO8LS11LS132LS107LS257LS151LS194LS139LS283LS367LS166LS377LS368LS86

4.99.35.35.80.35.90.65.90.60.95.80

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51/4 Mitac Disk Drivewith Controller Card $339W

51/4 double head Panasonic slim DirectDrive $299

51/4 IBM Compatible Slim Drive(case not included) $329

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40/80 column automatic display devices. easy to install and simple to use. software determines to show 40/80 column. full instructions and illustration provided. inexpensive device made in Canada $19.95

1. 52 function numeric keyboard (electronic touchupper/lower case)

2. 5' Floppy Disk Case (storage up to 150diskettes) $39.95

3. YVE High Res non -glare Amber Monitor $159.00net, 4051 Sheppard Avenue East (at Kennedy), Agincour

1.40-80 Column Switch2. Color R.F. Modulator3. Joystick (Self -centering)two adjustable controlsa) Parallel Printer Cardb) 16K RAM Cardc) 80 Column Cardd) Disk ControllerCarde) Z80 Cardf) Communication Card

$5.00$14.00$39.00

$69.00$59.00$79.00$55.00$60.00$67.00

A. 6502 48K KIT or (A&T) $499.00B. 6502 64K KIT or (A&T) $539.00C. 6502 64K built in Z80 or (A&T) $699.00ITEMS A,B & C Comes with case andnumeric keypad, gold (hydro approved 51amp power supply)D. 5 amp Teapo Black PowerSupply $99.00Quality IC SocketsDouble Side 2`/pinWe repair Power Supply and 6502 Boards

GOLD Switching Power $95.00Supply(+5V, 5 AMP, +12V, 2.5AMPS, - 5, 1/4 AMP, - 12V-'/x AMP). Heavy duty.Hydro approved. Run 2drives and lots ofperipherals.90 Days Warranty.

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Battery Condition andTerminal VoltageThe 12 V battery, in its many forms, is apretty well universal source of mobile orportable electric power. There are lead -acidwet cell types, lead -acid gel electrolyte (seal-ed) types, sealed and vented nickel cad-mium types, and so on. They are to befound in cars, trucks, tractors, portablelighting plants, receivers, transceivers, air-craft, electric fences and microwave relaystations - to name but a few areas.

No matter what the application, theoccasion arises when you need to reliablydetermine the battery's condition - itsstate of charge, or discharge. With wet celllead -acid types, the specific gravity of theelectrolyte is one reliable indicator.

6,, 1 3. 2 .1

O4

o' 12.6

However, it gets a bit confusing as therecommended electrolyte can have a dif-ferent SG depending on the intended use.For example, a low duty lead -acid batteryintended for lighting applications may havea recommended electrolyte SG of 1.210,while a heavy-duty truck or tractor batterymay have a recommended electrolyte SG of1.275. Car batteries generally have a recom-mended SG of 1.260. That's all very wellfor common wet cell batteries, but measur-ing the electrolyte SG of sealed lead -acid ornickel -cadmium batteries is out of the ques-tion.

With NiCads, the electrolyte doesn'tchange during charge or discharge.

Fortunately, the terminal voltage is agood indicator of the state of charge ordischarge. In general, the terminal voltage

12.0 10 HOUR DISCHARGE RATE

1143 HOUR DISCHARGERATE

108

O 2 4 6 8 10TIME (HOURS)

Fig. 1. Typical discharge characteristics of a 12 V (nominal) lead -acid battery.

to

10 HOUR DISCHARGE RATE

1111I3 HOUR DISCHARGE RATE

O 2 4 6 8 10TIME (HOURS)

Fig. 3. Typical discharge characteristics of a 12 V (nom.) nickel -cadmium battery (usually consisting of 10 cells in series).

15.6

514.44-I

O

313.2

12.6

120

of a battery will be at a defined minimumwhen discharged (generally between 10 and11 volts), and rise to a defined maximumwhen fully charged (generally around 15volts). Under load, the terminal voltage willvary between these limits, depending on thebattery's condition.

Hence a voltmeter having a scale'spread' to read between these two extremesis a very good and useful indicator of bat-tery condition. It's a lot less messy andmore convenient than wielding a hydro-meter to measure specific gravity of theelectrolyte!

The charge and discharge characteris-tics of typical lead -acid and sealed NiCadbatteries are given in the accompanyingfigures.

CHARGING RATEREDUCED

RAPID GASSINGOCCURS

0 2 To 1 16TIME (HOURS)

Fig. 2. Charging characteristics of a 12 V (nom.) lead -add bat-tery. The 'kink' in the curve near 6 hrs is explained in the text.

04-0> 1

f 1 4-

I-1 3

2 4 6 8 10TIME (HOURS)

Fig. 4. Typical charging characteristics of a 12 V NiCad battery(10 cells) charged with a constant current at one -tenth ratedcapacity (0.10.

Note that the fuse (to protect the pro-ject) is inserted in an in -line holder in theexternal connecting leads.

CalibrationFor this you will need a variable powersupply covering 10 to 15 volts and a digitalmultimeter (borrow one for the occasion).

First set the 10 V point. Connect thedigital multimeter across the power supplyoutput and adjust the power supply to ob-tain 10.00 volts. Set the mechanical zeroon the meter movement to zero themeter's pointer. Connect the unit to thepower supply output and adjust RV1 tozero the meter needle.

Next, set the power supply to obtain15.00 V. Now adjust RV2 so that the

meter needle sits on 15 V (full scale).Check the meter reading with the powersupply output set at various voltagesacross the range. We were able to obtainreadings across the full scale within ±half a scale reading ( ± 50 mV). With a 2%meter, the worst error may be about ±one scale division.

When set up, our unit drew 12.5 mAmaximum current drain, which is pro-bably typical, but current drain may bearound 20 mA or so maximum. Note that,when the input voltage is below 10 V, themeter needle will move in the reversedirection.


Survey of 50 SystemsThis month, we conclude last .month's survey of fifty lower -costmicrocomputers by presenting six- " -

.:.,-,-,

ty higher -cost machines. As usual, .304.i.,-.8 Ai tatli '

..we apologise for any inaccuracies, ............

,-,-,:- ---7--40.,

and we point out that prices mayvary from store to store. Happy 1,4 3 -.sai

System: Orion I A IaaWM0PWSa91 HiW4'. Ili VIdrooling. Operating System:Processors:

CP/M280A

era; AL AV ., OP fill . a a . 1111 . , A040'------- RAM: 64K

Printer I/O: S & 2 ExpDisk Drives Inc: Two 51/4" floppyScreen Format: 80x24 System: AJILE (portable)Graphics: N/A Operating System: MS DOSSound: N Processors: 8088Colour: N RAM: 256KKeyboard: Detachable Printer I/O: S & P Exp ModuleSoftware Included: CP/M Disk Drives Inc: One 51/4" DS DD floppy

ASSOrIlATE' Software Available: Extensive Screen Format: 80x25Primary Market: Business Graphics: 640x250Manufacturer: DY-4 Systems Inc. Sound: Programmable

i Available From: Prelco Electronics Colour: NPrice: $4500.00 Keyboard: DetachableOther: Multi-user capabilities Software Included: Basic, In:Scribe, Multiplan and

----7 CommunicationsSoftware Available: Extensive, IBM Comp at BIOS

System: Associate Primary Market: BusinessOperating System: CP/M

.

Manufacturer: BYTEC Management Corp.Processors: 280A Available From: Anderson Jacobson Ltd.RAM: 65K i Price: $4285.00Printer I/O: 2 SDisk Drives Inc: 2 DS DD 51/4" floppy

Other:

Screen Format: 80x25Graphics: 32 Graphics CharactersSound: N .11010. WSColour: NKeyboard: Integrated -Software Included: Microptan, Spellbinder, acc

pak System: Columbia VP-

Software Available: Extensive Operating System: CP/M-86, MSDOS III.Primary Market: Business or Personal Processors: 8088Manufacturer: Associate RAM: 128KAvailable From: Datacalc Technology Ind Corp. Printer I/O: S & PPrice: 54495.00 Disk Drives Inc: Two 1/2 height DSDD floppyOther: Screen Format: 80(40)x25

Graphics: 640x200Sound: YColour: N System: Canon AS -100Keyboard: Detachable Operating System: CP/M or DOS

82 Software Included: Perfect Series Fast Graphics,BASIC A

Processors:RAM:

8088128K

Software Available: Extensive Printer I/O: Opt S or PPrimary Market:Manufacturer:

BusinessColumbia Data Systems

Disk Drives Inc: Opt 5" or 8" floppy or 5"hard

Available From: Hamax Data Systems Screen Format: 80x25Price: 54495.00 Graphics: 640x400

s.Other: Portable, IBM PC software

compatibleSound:Colour:

NOpt

Keyboard: Detachable

System:Operating System:

Xerox 16/8 Prof. CompSupports CP/M-80, CP/M-86111111111111111111P----------NI

Software Included:Software Available:Primary Market:

2 BASICsExtensiveBusinessManufacturer:

& MS DOS CanonProcessors: 8086 & 280A Available From: Canon Canada Inc.

System: BASIS 108 RAM: 128K Price: $3200.00Operating System: BASIC Printer I/O: S & 13 Other:Processors: 6502 & 280ARAM: 64K

Disk Drives Inc: Opt 2 floppy or I hard, I flop -py

Printer I/O: P, S & 6 Exp Screen Format: 80x24Disk Drives Inc: Mounting for two 51/4" floppy Graphics: OptScreen Format: 80(40)x24 Sound: NGraphics: 280x192 Colour: N System: Heath HZ -89Sound: Y Keyboard: Detachable Manufacturer: HeathkitColour: Y Software Included: BASIC Available From: HeathkitKeyboard: Detachable Software Available: Extensive, supports CP/M-80, Price: $2295.00Software Included: BASIC CP/M-86, MSDOS Other: Kit version of Zenith Z-89Software Available: Extensive Primary Market: BusinessPrimary Market: Business Manufacturer: Xerox System: Heath HZ -I00Manufacturer: BASIS Inc. Available From: Xerox Stores Manufacturer: HeathkitAvailable From: Computer Systems Design Price: Announced in Sept. Available From: HeathkitPrice: $4000.00 Other: Stand-alone or workstation Price: $3499.99Other: Apple compatible capabilities Other: Kit version of Zenith Z-100

26- DECEMBER-1983-ETI

Computer SurveySystem:

Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:Available From:Price:Other:

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:AYailable From:Price:

Computer Devices DotPortableMS DOS8088128K2STwo 31/2" SS DD floppy80x251056x254NNDetachableMS DOSExtensiveBusinessComputer DevicesDatamexN/APrinter included in price

Kaypro IICP/MZ8064K2 S & PTwo 51/4" floppy80x24N/ANNDetachableSBASIC, Profitplan, SelectExtensiveBusinessKay ComputersComputron$2795.00

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:Available From:Price:Other:

Sharp PC 5000MS DOS8088 & C-MOS128KS

Opt 128K Bubble Cartridge80x8 LCD640x80NNIntegratedMS DOS, BASICExtensiveHome or BusinessSharpTotal Office Systems Inc.To be announced in Sept.Portable & printer included

System: Sony SMC-70Operating System: CP/MProcessors: Z80ARAM: 64KPrinter I/O: S, P & 5 ExpDisk Drives Inc: Opt SS DD 31/2" floppyScreen Format: 80x25Graphics: 640x400Sound:Colour: OptKeyboard: Detachable, QwertySoftware Included: CP/MSoftware Available: ExtensivePrimary Market: BusinessManufacturer: SonyAvailable From: Total Office SystemsPrice: $4900.00

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen FormaGraphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manuf acturer:Available From:Price:

MAGICCP/MZ80A64KS&PDSDD IBM Media compatible80x2496 Graphic CharactersNNDetachablePerfect Writer/Calc/Spell/FileExtensiveBusinessMagic Computer Co.Micro Bazzar$2,695.00

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:

Software Available:Primary Market:Manufacturer:Available From:Price:

Nelma PersonaCP/MZ80A64K2 S & PTwo 51/4" floppy80x24OPTNNDetachableWordstar, Calcstar and Com-munication SoftwareExtensiveBusinessNelma DataComputerland$2995.00

System: Pronto 16/10Operating System: MS DOSProcessors: 80186 (16 Bit)RAM: 128KPrinter I/O: 2 S, P & 4 ExpDisk Drives Inc: Two 51/4" floppyScreen Format: 80x25Graphics: Opt 640x480Sound:Colour:Keyboard: DetachableSoftware Included: BASIC, word processor and

spread sheetSoftware Available: ExtensivePrimary Market: BusinessManufacturer: Pronto Computers, USAAvailable From: To be announced in Sept.Price: N/A

System:

Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:Available From:

Price:

NEC Advanced PersonalComputerCPM, MSDOS8086128KS&POne or Two 8" floppy80x25640x475 Display WindowY

OptDetachableCP/M and MSDOSExtensiveBusinessNECMicrocomputers of CanadaInc.$4 95.00

System: NCR Decision Mate VOperating System: ChoiceProcessors: Z80 & 8088RAM: 64KPrinter I/O: S & PDisk Drives Inc: 2 flex or I flex & I hardScreen Format: 80x24Graphics: 640x400Sound:Colour: OptKeyboard: DetachableSoftware Included: BASIC, Financial & Word Pro-

cessor ProgramsSoftware .Available: ExtensivePrimary Market: BusinessManufacturer: NCRAvailable From: SGV MarketingPrice: $4495.00Other: Choice of CP/M-80, CP/M-86

or MS DOS


Computer Survey

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:

Primary Market:Manufacturer:Available From:Price:Other:

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:Available From:Price:

TI Professional

808864KS & 5 Exp320K floppy80x25720x300NOptDetachable

Supports MSDOS, CPM80,CPM86, USCDBusinessTexas InstrumentsLanpar$3975.00Voice management systemavailable

Tomcat PCX 1600CP/M & MSDOS8086 & Z80A128KS&PTwo 51/4" DS DD floppy80x25640x400NNDetachableCP/M & MS DOSExtensive, IBM CompatibleBusinessTomcatTomcat Computers$3995.00

System: Osborne ExecutiveOperating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:


CPM & UCSDZ80A128K2STwo 51/4" floppy80x24

NNIntegratedWordstar, Mailmerge, Super-calc, Personal Pearl, C & MBASICExtensiveHome or BusinessOsborne CanadaLanpar$3495.00

System:Operating System:Processors:RAM:Printer I/0:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:Available From:Price:Other:

Sord M23PCP/M CompPips128K2S, P & 3 ExpTwo floppy80x25 monitor640x200NOptIntegratedBASIC, spread sheetExtensiveBusinessSordMicos Computer Systems Inc.$2995.00Opt colour/green/LCD display


Software Available:Primary Market:Manufacturer:Available From:Price:Other:

Telcon ZorbaCP/MZ80A64KIEEE, P & STwo 51/4" DS DD floppy disks80x25N/ANNDetachableWitrdstar, Mailmerge, Calcstar,BASICExtensiveBusinessTelcon Ind. Inc.Micro Bazzar$2995.00

System: Televideo TS 1603Operating System: CP/MProcessors: 8088RAM: 128KPrinter I/O:Disk Drives Inc: Two 51/4" floppyScreen Format: 80x24Graphics: OptSound:Colour:Keyboard: DetachableSoftware Included: CP/M-86 & MMM Ost

Operating SystemSoftware Available: ExtensivePrimary Market: BusinessManufacturer: TelevideoAvailable From: DatamexPrice: $4420.00


Sharp YX 3200CP/M & FDOSYX-320064KP & S ExpOpt 51/4" or 8" floppy80x25N/ANNIntegrated2 BASICSExtensiveHome or BusinessSharpTotal Office Systems$2395.00

System: Televideo TS 803Operating System: CP/MProcessors: Z80ARAM: 64KPrinter I/O:Disk Drives Inc: Two 51/4" floppyScreen Format: 80x24Graphics: 640x240Sound:Colour:Keyboard: DetachableSoftware Included: CP/MSoftware Available: ExtensivePrimary Market: BusinessManufacturer: TelevideoAvailable From: DatamexPrice: $3704.00


Sord M68

MC68000, Z80A256K2 S, P & IEEETwo 5" mini floppy80x25640x400NOptDetachableNot availableExtensiveBusinessSordMicos Computer Systems Inc.Announced in Sept.


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As part of your training, you'llbuild your own 25" Heath/Zenith colorTY a state-of-the-art unit with infraredremote tuning, programmable channelselection, and the incredible space phone

Learn by doing with NRI hands-on projects andprofessional instruments that you use and keep.

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Exclusive NRI Training onVideotape

In addition to profusely illustratedlessons, you get NRI Action Videocassettes. . . videotaped lessons that show yougraphic presentations of electronic sys-tems, vivid closeups of servicing tech-niques and professional "shortcuts" tostudy and replay as often as you want.

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come a top technician, we get you readyfor independence. NRI Video/Audio ser-vicing gives you a great new way to earnextra money doing part-time servicingfor appliance and department stores . . .

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Mail Card TodaySend the postage -paid card for our

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im or telephone 416-293-8787

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Computer Survey

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Formal:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:Available From:Price:

Tomcat 3000MSDOS, CP/M-80, CP/M-868086 & Z80A128K2S8" floppy, 51/4" hard80x25640x400NOptDetachableCP/M-86, CP/M-80, MS-DOSExtensiveBusinessTomcatTomcat ComputersN/A

System: Intertec SUPERBRAIN II JROperating System: DOS & CP/MProcessors: Twin Z80ARAM: 64KPrinter I/O: 2 SDisk Drives Inc: Two 51/4" floppyScreen Format: 80x24Graphics: N/ASound:Colour:Keyboard: IntegratedSoftware Included: CP/M, DOS, BASICSoftware Available: ExtensivePrimary Market: BusinessManufacturer: Intertec Data SystemAvailable From: E.M.J. Data SystemsPrice: $2495.00

i****.'ilft

System: Commodore BX 128-80Operating System: CBMProcessors: 6509 & 8088RAM: 128KPrinter I/O: IEEE & SDisk Drives Inc: Opt disksScreen Format: 80x25Graphics: 720x350Sound:Colour:Keyboard: DetachableSoftware Included: N/ASoftware Available: ExtensivePrimary Market: BusinessManufacturer: CommodoreAvailable From: Local DealersPrice: N/AOther: Also available with 256K

System: TRS-80 Model 4Operating System: TRS DOSProcessors: Z80ARAM: 64KPrinter I/O:Disk Drives Inc: Two SSDD 51/4" floppyScreen Format: 80x24Graphics: Opt 640x240Sound: ProgrammableColour:Keyboard: IntegratedSoftware Included: TRS DOS, BASICSoftware Available: COMP CP/M, LDOSPrimary Market: BusinessManufacturer: TandyAvailable From: Radio ShackPrice: $2999.00Other:

System: IBM PCOperating System: DOS, UCSD P -System &

CP/M-86Processors: 8088 System: Zenith Z-89RAM: 64K Operating System: ChoicePrinter I/O: 13 Exp. Processors: Z-80Disk Drives Inc: One 160KB Diskette RAM: 48KScreen Format: 80x25 Printer I/O: YGraphics: 640x200 Disk Drives Inc: 100KSound: N Screen Format: 80x25Colour: Opt. Graphics: Character symbolsKeyboard: Detachable Sound: NSoftware Included: Operating Systems Colour: OptSoftware Available: Extensive Keyboard: IntegratedPrimary Market: Business Software Included: CP/M and/or ZDOSManufacturer: IBM Software Available: ExtensiveAvailable From: Local Dealers Primary Market: BusinessPrice: $3,200.00 Manufacturer: ZenithOther: Opt. auxiliary storage with Ex- Available From: Local dealers

pansion unit. Price: $3745.00

System: Zenith Z-100Operating System: ChoiceProcessors: 8088 & 8085RAM: 128KPrinter I/O: 2S&IPDisk Drives Inc: One 51/4" floppy DS DDScreen Format: 80x24Graphics: 225x640Sound:Colour: OptKeyboard: IntegratedSoftware Included: CP/M and/or ZDOSSoftware Available: ExtensivePrimary Market: BusinessManufacturer: ZenithAvailable From: Local dealersPrice: $4675.00

System: Apple IleOperating System: DOSProcessors: 6502ARAM: 64KPrinter I/O: 8 Exp. slotsDisk Drives Inc: Opt. 51/4" floppyScreen Format: 80)(24Graphics: 280x192Sound:Colour:Keyboard: IntegratedSoftware Included: DOS, BASICSoftware Available: ExtensivePrimary Market: BusinessManufacturer: Apple CanadaAvailable From: Local DealersPrice: 52895.00Other: $2995.00 - 128K

System: Heath HZ -89Manufacturer: HeathkitAvailable From: HeathkitPrice: $2295.00Other: Kit version of Zenith Z-89

System: Heath HZ -100Manufacturer: HeathkitAvailable From: HeathkitPrice: $3499.99Other: Kit version of Zenith Z-100



Software Available:Primary Market:Manufacturer:Available From:Price:Other:

Columbia VPCP/M-86, MSDOS8088128KS&PTwo 1/2 height DSDD floppy80(40)x25640x200YNDetachablePerfect Series Fast Graphics,BASIC AExtensiveBusinessColumbia Data SystemsHamax Data Systems54495.00Portable, IBM PC softwarecompatible

System: Olivetti M20Operating System: PCOSProcessors: Z8001RAM: 128KPrinter I/O: S, P & 5 Exp.Disk Drives Inc: DDDS 51/2" floppyScreen Format: 80x25Graphics: 512x256Sound:Colour: Opt.Keyboard: IntegratedSoftware Included: PCOS, BASIC, TutorialsSoftware Available: ExtensivePrimary Market: BusinessManufacturer: OlivettiAvailable From: KSO Sales Agency Ltd.Price: 54170.00


Software Available:Primary Market:Manufacturer:Available From:

Price:

Olympia "People"CP/M & MSDOS8086128KS&PTwo floppy disk drives80x25600x485NOptDetachableWordstar, Supercalc, D BASEII

ExtensiveHome or BusinessOlympia Int.Olympia Bus Machines CanLtd.55950.00

System:Operating System:Processors:RAM:Printer I/O:Disk Drives Inc:Screen Format:Graphics:Sound:Colour:Keyboard:Software Included:Software Available:Primary Market:Manufacturer:Available From:Price:Other:

HyperionMS DOS8088256KS, P & IEEETwo 51/4" DS DD floppy80x25640x250ProgrammableN

DetachableMultiplan, text editor, 2 othersExtensiveBusinessBYTEC Mang. Corp.Computerland54950.00IBM compatible, portable



Hewlett-Packard 200 Model 16OptMC68000128KS & IEEE

80x25300x400NN

DetachableChoice of BASIC, HPL orPASCALExtensiveBusinessHewlett PackardHewlett Packard$6079.00


Victor 9000CP/M, MSDOS8088128K2 S & 2 PTwo 5" SS floppy132(80)x25800x400NN

DetachableOperating systems, BASICExtensiveBusinessVictorCompucollege Stores55495.00

System: Commodore Executive 64Operating System: BasicProcessors: 6510RAM: 64KPrinter I/O: S & IEEEDisk Drives Inc: 170K single disk driveScreen Format: 40x25Graphics: 320x200Sound:Colour:Keyboard: DetachableSoftware Included: Not finalizedSoftware Available: CBM 64 software compatiblePrimary Market: BusinessManufacturer: CommodoreAvailable From: Local dealersPrice: To be announced in the FallOther: Portable

71Wrainvitei

System: Epson QX-10Operating System: ValdocsProcessors: Z80ARAM: 256KPrinter I/O: S, P & 5 ExpDisk Drives Inc: Two 51/4" DS DD floppyScreen Format: 80x25Graphics: 640x400Sound:Colour:Keyboard: DetachableSoftware Included: Indexer, Word Processor, Mai

System, GraphicsSoftware Available: ExtensivePrimary Market: BusinessManufacturer: EpsonAvailable From: ESSNAPrice: 543(0.00Other: CP/M Compatible


Hitachi MB 16001DOS, CP/M8088128KS, P & 5 ExpDS DD 8" floppy80x25640x400NOptDetachableMS DOS, CP/M, BASICExtensiveBusinessHitachiHitachi (HSC) Canada In.55000.00

ETD -DECEMBER -1983-31

Computer Survey

System: Cromemco C-10SPOperating System: CP/M COMPProcessors: Z80ARAM: 64K

....iv=

Printer I/O:Disk Drives Inc:

S & PTwo 51/4" floppy DSDD

1

Screen Format:Graphics:Sound:

80x25N/AN

Colour: N_ Keyboard: DetachableSoftware Included: Word Processor, Spreadsheet &ll'A

al ''- Software Available:Primary Market:

BASICExtensiveBusiness

--- .. vire,:*.it..,Manufacturer-Available From:

CromemcoNSN Options

Price: $2495.00

System: Corona Portable System: Corona Personal System: Toshiba T 100Operating System: MSDOS Operating System: MSDOS Operating System: CP/MProcessors: 8088 Processors: 8088 Processors: Z80ARAM: 128K RAM: 128K RAM: 64KPrinter I/O: S& P Printer I/O: S and P Printer I/O: S& PDisk Drives Inc: One half size floppy Disk Drives Inc: One SS DD floppy Disk Drives Inc: Two 51/4" DS DD floppyScreen Format: 80x24 Screen Format: 80x25 Screen Format: 80x25Graphics: 640x325 Graphics: 640x325 Graphics: 640x200Sound: Y Sound: Y Sound: NColour: N Colour: N Colour: OptKeyboard: Detachable Keyboard: Detachable Keyboard: DetachableSoftware Included:Software Available:

Multimate, 2 TutorialsExtensive, 4 IBM Compatible

Software Included:Software Available:

Multimate, 2 TutorialsExtensive, 4 IBM Compatible

Software Included: 2 BASICS, Word Processor,Spread Sheet & Data Base

slots slots Software Available: ExtensivePrimary Market: Business Primary Market: Business Primary Market: BusinessManufacturer: Corona Manufacturer: Corona Manufacturer: ToshibaAvailable From: Scarsdale Computers Available From: Scarsdale Computers Available From: PWT Computer GroupPrice: 53880.00 Price: $3880.00 Price: $2995.00

Other: Can mix text and graphics

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System: Apple IIIOperating System: SOS

Processors: 65028RAM: 256KPrinter I/O: S & 4 Exp.Risk Drives Inc: One 51/4" DD floppyScreen Format: 80x24Graphics: 560x192Sound: Opt.Colour: Opt.Keyboard: IntegratedSoftware Included: SOSSoftware Available: ExtensivePrimary Market: BusinessManufacturer: AppleAvailable From: Local DealersPrice: $3895.00

ADDRESSES:

Anderson Jacobson Canada Ltd., 32 Don Mills Rd.,Markham, Ontario, L3R 1C2. (416) 475-5510.

Apple Canada, 875 Don Mills Rd., Don Mills, On-tario, M3C 1V9. (416) 444-2531.

Canon Canada Inc., 3245 American Dr., Mississauga,Ontario, 1.4V 1N4. (416) 678-2730.

Commodore Business Machines, 3370 PharmacyAve., Agincourt, Ont, MIW 2K4. (416) 499-4292.

Computer Land, 3761 Victoria Park #5, Scarborough,Ontario, MIW 2S6. (416) 497-5722.

Computer Systems Design, P.O. Box 32, LakeWilcox, Ontario, LOG 1XO. (416) 773-0467.

Computron, 55 Torbay Road, Markham, Ontario,L3R 167. (416) 447-0828.

Data Cale Technology Ind. Corp., 224 Slater Rd.,Cranbrook, British Columbia. (604) 489-5343.

Datamex, 14 Leswin Rd., Toronto, Ontario, M6A1K2. (416) 781-9135.

EMJ Data Systems, 79 Regal Rd., Unit 5, Guelph,Ontario, NIK 1B6. (519) 837-2444.

Essna Services Ltd., 31 Progress Court, Unit 1, Scar-borough, Ontario, MIG 3V5. (416) 438-8060.

Hamax Data System, 1262 Don Mills Rd., Don Mills,Ont., M3B 2W7. (416) 447-5587.

Heathkit, 1478 Dundas St. East, Mississauga, On-tario, LAX 2R7. (416) 277-3191.

IBM Canada Ltd., 3500 Steeles Ave. East, Markham,Ontario, L3R 2Z1. (416) 474-2111.

KSO Sales Agency Ltd., 1262 Don Mills Rd., Unit 72,Don Mills, Ontario, M3B 2W7. (416) 441-2869.

Lanpar, 85 Torbay Rd., Markham, Ontario, L3R167. (416) 475-9123.

Micro Bazaar, 23 Westmore Dr., Unit 5, Rexdale, On-tario, M9V 3Y7. (416) 745-4740.

Micos Computer Systems Inc., 1295 Eglinton Ave.East, Cooksville, Ontario, LAW 3E6. (416) 624-0320.

Micro Computers of Canada Inc., 3410 MidlandAve., Unit 6, Scarborough, Ontario. (416) 293-3885.

NSN Options, 250 Wyecroft Rd., Unit 11, Oakville,Ontario, L6K 3T'7. (416) 842-6530.

Prelco Electronics, 2767 Thamesgate Dr.,Mississauga, Ont., L4T 1G2. (416) 678-0401.

PWT Computer Group, 1305 Matheson Blvd.,Mississauga, Ontario, LAW IR1. (416) 624-7455.

Radio Shack Computer Centre, 329 Bay St., Toronto,Ontario. (416) 365-7207.

Scarsdale Computers, 1 Scarsdale Rd., Don Mills, On-tario, M3B 2E2. (416) 441-1900.

SGV Marketing 1520 Trinity Dr. Unit 16, Mississauga,Ontario, L5T 1T6. (416) 673-2323.

Tomcat Computers of Canada Inc., 6299 Airport Rd.Suite 404, Mississauga, Ontario, L4V 1N3. (416)673-2040.

Total Office Systems Ltd., 1050 McNicoll Ave., Unit14, Scarborough, Ontario, MIW 2L8. (416) 493-3575.

Xerox Store, 110 Eglinton Ave. East, Toronto, On-tario. (416) 482-6111.

Zenith Data Systems, 1020 Islington Ave., Toronto.Ontario, M8Z 5X5. (416) 231-4171.

FASTRONcompuTER INC.250 DUNDAS ST. W. (AT UNIVERSITY) TORONTO, ONTARIO M5T 2Z1

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6502 CPU 48K $297.00 12" Amber $189.00Numeric Keyboard $ 99.00 Nonglare Monitors5A Power Supply $ 88.00 12" Disco Green $189.00Numeric Case $ 66.00 12" Amber $198.00Complete Kit $550.00

Epson Printer $499.00Disk Controller $ 59.00 CP-80 $550.0016K RAM Card $ 59.00 Slim Drive $315.00Z80 CP/M $ 73.00 Mitac Drive $315.0080 Col. Card $ 85.00 Micro-Sci $325.00Printer Card $ 78.00

Memorex Disk (10) $ 29.75Voice Synthesizer $ 75.00 BASF Disk (10) $ 29.75Eprom Writer $ 98.00 CDC Disk (12) $ 29.50Wild Card $ 98.00 Disk Bank $ 3.99RS232 Card $ 88.00 Printer Paper 14/MSystem Fan $ 50.00 Joystick $ 27.00

Game Tape $ 7.00 IBM PC with 320K Drive CallGame Disk $ 10.00 2nd 320K Drive $ 335

Microsoft Mouse $ 252

ZENITH MONITORS Microprofessor 64K . $ 67512" Green $129.00 Magic Computer $ 2,20512" (New) Green $149.00 Coleco Adam $ 788

MAIL ORDERSAdd $3.00 for shipping & handling. Ontario residents add 7% P.S.T. VISA,

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COMPUTERS' SOFTWARE' COMPONENTS' ACCESSORIES' BOOKS' RENTAL


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Designing Micros Part 4Last month, Owen Bishopexplained what a ROMchip is. This month, hetells you why. Read on.

A short program which enables the MPUto get started on its more important tasksis called a boot -strap program. It helps theMPU pull itself up by its bootstraps!Since such a program must already be inthe computer from the moment power isswitched on, the obvious course is to placethis program there permanently in ROM.Most computers have additional ROMprograms to instruct the MPU how to doother kinds of routine jobs, such as sendoutput to the display. Quite often amessage such as "APPLE II' or`MEMORY SIZE?' is placed on thescreen when the computer is switched on.The program to do this is held in ROM.The complete program may occupy a fewkilobytes of memory. Such a program isgenerally called a monitor program. Thisis another use of the word 'monitor', thename usually given to a purpose-builtcomputer video display (as opposed to adomestic TV set being pressed into serviceas a computer display).

The monitor program is usually writ-ten in machine code (see October'sarticle), for this is the most compact wayof instructing the MPU and allowing it tooperate at its maximum speed. Most com-puter users prefer to communicate withthe MPU by using a high-level language,such as BASIC. MPUs do not understandBASIC, so a program written in machinecode is needed to interpret programs writ-ten in BASIC. Then the MPU can unders-tand what it must do. The interpretingprogram (or interpreter) can be loadedfrom tape or disk into RAM, but sincesuch a program is likely to be requiredevery time the computer is used, it is moreconvenient to hold it in ROM. Thus theROM of a microcomputer may have, say,12K of ROM which holds all the routines(in machine code) for interpreting BASICcommands and executing them.

When buying a microcomputer it isessential to find out whether you need tobuy BASIC on a disk and load it everytime you want to use it, or whether theBASIC is resident in ROM. Usually thememory space quoted for a computer is

the amount of RAM it has. A computerwhich is listed as having 48K will allowyou to use almost the whole of that foryour programs if its BASIC is in ROM.On the other hand, if the computer has56K but no resident language, thelanguage may use up 12K of that spacewhen loaded in RAM, leaving you withonly 44K for your own programs.

A Change Of CharacterAnother use for ROM is to hold tableswhich are to be frequently used by thecomputer. A good example is the`character generator' ROM. Before it canput a character onto the screen, the MPUmust find out exactly what pattern of dotsare required to produce the letter,numeral, or symbol that is to bedisplayed. These patterns are held in thecharacter generator ROM. The MPU

reads the appropriate pattern from theROM and sends it to the video area ofRAM, causing the character to bedisplayed.

It is feasible to manufacture severaldifferent character generator ROMs, eachcontaining a different selection ofcharacters. There can be different type-faces, or the selection of letters and sym-bols can be chosen according to the coun-try in which the computer is to be used.For example, Video Inc. manufactures aseries of such EPROMs for the Apple IIincluding the French, German, Spanishand Katakana (Japanese) alphabets, andone holding mathematical and Greek sym-bols.

Another type of plug-in ROM whichis widely used holds a complete gamesprogram, educational program, or utilityprogram. Instead of loading the program

AO 0410A2 0A3 0A4 0A5 0A60A7 0A80A90

A1004110A1204130414 0415

ROMs OR PROMS

DECODER74LS138

G1

MREQ .-0 G2B-a G2A

0v

AO

AlA2A3A4A5

ROM 0

A7

A8A9

A10A

DID2

D3D4

0506D7

TRISTATE OUTPUTS

A SELECTB INPUTS

YO D

VIY2 D-

OUTPUTS Y3 °-V4V5 D-V6 D-

INNPAL

IBTLYSE7

AO

AlA2 DO

A313312

A4AS

ROM 1 D3

AlA8A9A10All E

D5

D6

D7 U.

AO

AlA2 DO

A3 DIA4 D2

A6D3

11n--A7 05A8 D6

A9 D7

410All

CS

0 . 0n it I NA el 00 0 0 0 0 0 0

DATA BUS

Fig. 1. Addressing three 4K ROMs.


TABLE 1ADDRESS RANGE

ROM NO. DECIMAL HEXADECIMAL BINARY

0 0 to 4095 0000 to OFFF 0000 0000 0000 0000 to

1 4096 to 8191 1000 to 1FFF0000 1111 1111 11110001 0000 0000 0000 to

2 8192 to 12287 2000 to 2FFF0001 1111 1111 11110010 0000 0000 0000 to0010 1111 1111 1111

from tape or disk, the user simply plugs ina module containing a pre-programmedROM. The Atari and Tandy TRS-80 Col-our Computer are examples of machineswith this facility, as are many of the morespecialized TV games machines.

Addressing MemoryWe have often referred to the MPU ad-dressing a given byte in memory at a par-ticular address, without giving any indica-tion of how this is done. Let us look intothis in a little more detail. As an example,consider a ROM (it might be a regularmask -programmed ROM or some type ofPROM) which stores 4 kilobytes. Each bitof these 4096 bytes is represented by amemory cell. This very -large-scale inte-grated circuit (VLSI) therefore contains32768 memory cells, each consisting of atransistor which is set on or off depending

upon whether it corresponds to a 0 or a 1.It also contains the logic circuits requiredto ensure that when any one of the 4096possible combinations of voltage levels(the 4K addresses) is put on the lower 12lines of the address bus (lines Al 1 to A0),the eight bits of information stored by thecorresponding eight transistors will begated onto the eight lines of the data bus.

The extreme complexity of such a cir-cuit is difficult to imagine, yet it is com-monplace on the computer circuit board.To accommodate a monitor program anda resident language we may need threesuch ICs, giving a total ROM memory of12K. Suppose that this is to run from thevery bottom of the computer's memory(from address 0000 onwards). The ad-dresses corresponding to the three ICs willbe shown in Table 1. From the binary ad-dress it is clear that the lower 12 address

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lines are responsible for differentiating be-tween all the addresses held in a singleROM. The state of the upper four addresslines (A15 to Al2) tell us which, if any, ofthe three ROMs is to be addressed at anyparticular time. Thus the address 4295(1007 in hex) appears on the bus as:

0001 0000 1100 0111

and refers to ROM1. The address 8391(2007 in hex) appears on the bus as:

0010 0000 1100 0111

and is located in ROM2. All three ROMsreceive the signals on lines All to A0.How can we ensure that only ROM1 re-sponds to the address 1007, while onlyROM2 responds to 2007?

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Designing Micros Pt. 4

The outputs of the ROMs to the databus are tri-state outputs. That is to say,they normally present a very high im-pedance; they are virtually disconnectedfrom the bus, and they are incapable ofeither sending or receiving signals. EachROM has one (more in some types) specialinput known as chip select (C S ). The barover the C S indicates that this is anactive -low input. When the C S input ismade low, data outputs go to a low -impedance state and whatever data is pre-sent on the set of cells currently being ad-dressed is put on to the data bus. Fig. 1

shows how we control which ROM is to beactive at any given time.

Go Low To GoThe function of the circuit is to enable oneROM at a time by making its C S inputgo low. The ROM to be selected is deter-mined by the signals present on the upperfour address lines and on a control linewhich indicates when the MPU is ready toread data. In the Z80 this is theMR E Q line, which is active -low. The74LS138 is a 3 -to -8 -line decoder which istypical of the ICs used for decoding ad-dress lines in computers.

Lines Al2, Al3 and A14 go to the A,B, and C inputs of this IC. Their states aretreated as a three -bit binary input. Out-puts YO to Y7 are normally high, but pro-vided that the IC is enabled, one of theoutputs is low at any one time, dependingon the binary input to A,B,C. Thus whenA is low, B is high and C is low, this cor-responds to 010 (equivalent to decimal 2),and output Y2 goes low. This makes theC S input of ROM2 low, so ROM2 isenabled while the other ROMs remaindisabled in the high -impedance state. Thelocation in ROM2 which is to be address-ed is then determined by the state of theother lines (All to A0) of the address bus.

The decoding of inputs A, B and C asdescribed above, takes place only if thedecoder itself is enabled. It has threeenable inputs, G1, G2A and G2B. Toenable the chip, GI must be high andeither G2A or G2B must be low. You willnotice the convention on the drawing thatsmall circles are drawn at G2A and G2B toindicate that they are active low. The out-puts also have these circles, for the samereason.

There are several possible ways of us-ing the enable inputs to make sure that thechip is enabled only when address lineA15 is low and the MR E Q line is lowtoo. The solution shown here is to NORAl5 and MR E Q together and feedthe result to Gl. This makes GI high onlyif both A15 and MR E Q are low. In-puts G2A and G2B are not used and aregrounded.

Let us sum up the procedure ofreading from ROM. In order to addressany particular cell of ROM, the MPU putsits address on the bus. In the example

given, the address will be received alonglines AO to All in all three ROMs. Thestates of lines Al2 to A14 are to be decod-ed by the 74LS138 and line A15 must below to allow the decoder to be enabled.Then the MPU takes its MR E Q outputlow to indicate that it wishes to read data.This makes the NOR gate output go low,enabling the decoder. One of its outputsthen goes low, enabling one of the ROMs.The ROM so addressed puts the data onthe bus and this is read by the MPU.

The procedure outlined above mustbe carried out according to a strict timeschedule. For instance, if the decoder actstoo slowly, the MPU may be trying toread data before it is there. Some mentionof this problem was made in Part 1, andwe shall discuss it again in connection withRAM, next month.

Fig. 2. A simple resetting circuit.

ROM At The Top?Readers who have taken the trouble tolook at the circuit diagram of a computerand compare it with Fig. 4 may find thatthe ROM of their computer does not ap-pear to be decoded to the low addresses inmemory. This is the case if the computerconcerned is based on the 6502 MPU.Unlike the Z80 and several other MPUs,the 6502 does not begin reading its pro-gram at 0000 after being reset. The 6502has the special feature of zero -page ad-dressing; this means that addresses in therange 0000 to 00FF can be addressed byusing the lower byte only (00 to FF). Thisgreatly simplifies and shortens programs,making this area of memory a very usefulplace in which to store frequently refer-red -to variables and tables. To take ad-vantage of this facility, this part ofmemory must be allocated to RAM. Con-sequently, it is better if ROM is located atthe top end (higher addresses) of memoryinstead. When the 6502 is reset, it firstreads the two bytes which are stored atFFFC and FFFD, addresses almost at thetop of memory. It is essential to placeROM so that it covers these addresses.

Memory cells FFFC and FFFD inROM contain the two bytes which are the

address of the beginning of the monitorprogram. In the Apple II with theAutostart ROM, for example, these bytesare 62 and FA, respectively. The 6502,having read these two bytes, sets its pro-gram counter to the address they indicate(FA62 in this example) and then goes tothat address to begin reading and ex-ecuting the monitor program.

Integrating ICsNowadays there is a move toward reduc-ing the number of ICs required in com-puter systems. This is particularly impor-tant for special-purpose computers thatare to be used in control applications,such as those in washing machines orvideo -recorders. The program requiredmay be relatively small (perhaps only 2Kor 3K) so there is no reason why the ROMshould not be accommodated on the sameslice of silicon as the MPU. If we haveROM, why not have RAM as well, andany other useful devices such as in-put/output ports and timers? A good ex-ample of this approach is the Zilog Z8`computer -on -a -chip'; a similar device isthe Mostek MK3870. The Z8 not only hasan MPU but also 2K of ROM, 128 bytesof RAM (enough to use as a 'scratch -pad'to hold temporary data), four eight -bitI/O ports, two counter/timers, and anasynchronous serial interface. The ROMin the Z8 has to be mask -programmed, sothis IC is not one that the hobbyist is like-ly to be using. The professional can obtaina version of the Z8 or the MK3870 with anEPROM mounted on it in piggy -backstyle. This can be programmed during thecourse of development and after all hasbeen settled, the final program can bemask -programmed into the internal ROMof the production version.

A special version of the Z8, known asthe Z8671, has the ROM pre-programmedwith a Tiny BASIC interpreter as well asits monitor program. This can be used asthe basis of a simple computer system. Ithas 144 bytes of RAM for use as a scratch -pad, but it can address up to 124K bytesof external RAM or ROM for the storageof programs. This version with its general-purpose BASIC in ROM has a wider ap-peal than custom -programmed versions,so it can be manufactured in quantity.Prices are falling and already severaldevelopment boards are on sale whichfeature this IC. The phrase 'chips witheverything' can now be taken to mean`chips with everything on them'!

Next month, RAM: Reading, 'Riting, butno `Rithmetic.


VIA E 11 60MHz OSCILLOSCOPE HM605

Viewing Hoods HZ47 $12.00

For HM203, HM204, HM605, HM705, HM808,HM312, HM412, HM512, and HM812

Scope Tester H Z60 $63.75

The HZ60 provides a fast -rising (-45ns) switchable1kHz/1MHz square -wave generator for checkingwide -band measuring amplifier systems and forprobe compensation. Three BNC-outputs providesignals of 20mVpp, 0.2Vpp and 2Vpp-±- 1%.

4 -Channel Switch HZ64 $585.00

Enables the simultaneous display of 4 individualsignals or 2 sums or 2 differences of signal voltageson an oscilloscope. Channel switching can beselected for chopped or alternate mode. Each chan-nel comprises a 12 -step frequency -compensated in-put attenuator with 1 M ohm II 30pF input im-pedance. Sensitivity range 5mV - 20V/div.in 1-2-5sequence. Bandwidth 4xDC-60MHz. Triggering (DC- 100MHz) is possible for each channel.As an additional advantage, the input sensitivity ofthe oscilloscope can be increased by the 10x gainof the HZ64.

Component Tester HZ65 SPECIAL $60.00

Indispensable for trouble -shooting in electronic cir-cuits. Single component and in -circuit tests areboth possible. The HZ65 operates with all scopes,which can be switched to X -Y operation (ext.horizontal deflection). Non-destructive tests can becarried out on almost all semiconductors, resistors,capacitors, and coils. Two sockets provide forquick testing of the 3 junction areas in any small'power transistor. Other components are connectedby using 2 banana jacks. Test leads supplied.

Examples of Test Displays:Short orcuit Capacitor 33µF Junction E -C

Carrying Cases

For HM203-1 and HM203-3For HM312, HM412, HM512,and HM705For HM307, HZ62, and HZ64For HM103For HM204-4, HM204,and HM605

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The multitude of operating modes of the HM605 make ita universal oscilloscope - one which satifies a wide variety oflaboratory demands. Its expanded Y-axis sensitivity of 1 mV/cm allows extremely small signals to be displayed. Despite thishigh sensitivity, vertical amplifier drift is extremely low. Verticaloverscanning of the usable screen area is indicated by LEDs. Abuilt-in delay line permits viewing of the trigger leading edge.

Triggering is possible up to at least 80 MHz. Triggeringfacilities allow, among other things, the display of two non -time -related signals. Line triggering, single sweep, and vari-able hold -off time are also available. A sweep range of from 5 ns/cm to 2.5sec/cm ensures high resolution as well as display ofextremely slow signals. Analysis of small signal sections of awaveform is possible using the sweep delay feature, whichallows X -expansion by 1000 or more.

A rectangular 14 kV CRT with an illuminated graticule pro-vides exceptionally bright, sharp diplays. The HM 605 incorpo-rates a switchable fast -rise -time 1 kHz/1 MHz square wavegenerator for high frequency probe compensation and systemchecks - a unique feature for scopes in this price range. Thisfeature makes it possible to check transmission performance ofthe Y -amplifier, compensation of modular attenuation probesand optimum utilization of the entire bandwidth of the instru-ment and probes.

As with all new HAMEG flat -line oscilloscopes, a compo-nent tester is also incorporated in the HM605. The outstand-ing price/performance ratio of this oscilloscope is not likely tobe matched by the competition in the near future.

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Product ReviewBrother EP20 Electronic Typewriter

Computer technology isadapted to the typewriter inthis tiny but versatile unit.

By Bill Markwick

THE BROTHER Company, well-knownfor its larger typewriters, has had the por-table EP20 on the market for a bit less thanone year. Its price of just under $300 aims itat the low -end portable market, but its uni-que features put it in a class by itself.

The first thing you'll notice about theEP20 is its tiny size (315 x 237 x 44 mm)which allows it to fit into a briefcase, andthe second is that it has a full-size QWERTYkeyboard that sits comfortably under thefingers for touch-typing. The keyboard hasall the functions of a larger typewriter: tabs,margins, backspace and so forth, and also asecond shift key which allows 44 specialcharacters, such as foreign language accentsand math symbols.

Getting acquaintedPower it up using the supplied AC

adaptor, or four D -cells, and insert thepaper. Press the paper -feed button, and the

platen winds it in for you; there's the usualpaper release lever for adjustments. Younow have three options via a slide -switch:You can type directly to the paper, as you'dexpect, or you can use the 16 -character cor-rection buffer before printout, or you canjust use the buffer for practice typingwithout printing. Select the correctionmode, which is the one you'll probably beusing the most, and begin. As you type, thecharacters march past in the little windowabove the keyboard. If you should changeyour mind before typing 16 characters, thereare control keys for moving the little cursorto insert and delete characters. When you'vetyped in the full 16, the miniature print headbegins to print out the first keystrokes thatyou entered. Towards the end of the line theentire buffer is printed and a little motorwhirs the print head back for another go.You soon get used to the fact that the key-board is 16 characters ahead of the printer,

and you'll soon be catching all your mis-takes before they reach the paper.

The print head holds the little ribboncassette. It uses a plastic film ribbon, andthis film is responsible for the very highreadability of the printout from the 5 x 7matrix. Unfortunately, it can't be rewound(all the carbon is transferred to the paper)and being so tiny, the number of pages youcan get from one cassette is about twelve orso.

The impression you'll be left with fromtyping away is the remarkable smoothnessand silence of the EP20. There's only aslight ticking noise as it prints out, and onlya gentle whir as the head returns to the left.Try putting in accents: type the one youwant and the cursor will wait until you typethe letter under the accent. Beautiful! Theonly drawback is that a 5 x 7 matrix can't doproper descenders, the part of the letter thatpokes down below the baseline; letters such

38-DECEMBER-1983-ETI Continued on page 76

Sord M-5 ReviewLike programming video games? Hatewriting assembler code? Have lots of

money to throw around? Anthony DeBoerlooks at the computer for you.

ONCE UPON A time, there was but onecomputer. It was lonely. Some time afterthis, however, there were many computersto keep it company, so many, in fact, thatthey had to be cloned to keep up with de-mand. Shortly after this, the Sord M-5 ar-rived on the scene.

Opening the box in which an M-5 ar-rives, you find a cute little computer,about the size of a good book (or a pair ofpaperbacks), nicely done up in two shadesof grey and one of yellow. Examining itmore closely, you find it has thoseeraserhead keys we've all come to knowand love, a space key instead of a spacebar, and an external power supply. Thejoysticks (the manufacturer calls themjoypads) are the flat pad variety that arerather cumbersome to use. The intrepiduser soon finds that the top back half ofthe machine's cover lifts off to reveal, yes,a cartridge slot. In other words, it looksmuch like your basic modern, mass-pro-duced microcomputer.

ill1111111111{011111111111111/,1111 19

Before we throw it in the corner withall the others of its ilk, let's give it half achance and turn it on. It is, in fact, notuntil you turn it on that the M-5 showsany redeeming features at all. Thismachine has an extremely fast, compactBASIC that enables one to write decentvideo games without having to use ma-chine code at all.

For $460, the purveyors of thismachine are willing to part with not onlythe machine itself, but also a pair ofjoypads, a BASIC -G cartridge, a case,and whatever other trivia is consideredneedful. This is rather steep for such asmall machine, but on the other hand, theprice might eventually come down.

EraserheadsThe keyboard is the standard QWERTYarrangement, with one major exception:the space bar is missing. One finds, all theway to the right, just under the return key,a key marked SPACE. One does get used


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90 KEY ULTRASLIM DETACHABLE KEYBOARD Besides the conventional 56 main key layout, the MPF-III comes with anumeric keypad, special function keys and user function keys.

36 TONE SOUND GENERATION CHIP The MPF-III has a 36 tone sound generation chip that can beprogrammed according to your musical tastes. Sounds emmitted include piano, bell, gunfire, bombing or laser.

7 INTERFACES FOR A WIDE ARRAY OF I/O DEVICES The MPF-III has a standard 7 interface port configuration that givesyou the ability to interface with disk drive, printer, cassette recorder, Z-80 CP/M card, Chinese character card and monitor or television.

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Sord Socius

to this after a while, but it's a problem atfirst. The keys themselves are of the darkgrey rubber pencil -eraser variety, each be-ing square (or in some cases rectangular),with the lower right-hand corner cut off(except for the keys all the way on theright side, for which it's the lower left-hand corner). The keyboard is quiteusable, although it's not exactly the ex-pensive professional variety you would ex-pect at the price given.

In addition to the usual SHIFT andCTRL keys, you get a FUNC key, whichallows access to a number of keywords.FUNC-A, for example, causes the word"AUTO" to appear, just as if you hadtyped the whole thing yourself. There arealso three modes: normal lower case,capitals, and graphics, this last allowingyou to type in the graphics symbols thatappear in yellow on the key caps.

Screen editing is also provided. Youcan move up to an offending line with thecursor arrows, delete things, insert things,and then hit return to re-enter the line.You soon discover that whenever you hitreturn, BASIC tries to act on the line youwere on, regardless of what it consists of.This is an advantage, in that you don'tneed to copy over an entire line to changeit, but can also be a disadvantage since itmakes it impossible to splice bits of dif-ferent lines together. It can also providethe occasional shock if you hit return overa line consisting of the word "NEW".Plug -insWith the review machine came five car-tridges: two BASIC's, two games, and aspreadsheet program.

The first BASIC, BASIC -I (meaning"Introductory"), seemed to be just a sim-ple beginner's version of the other,BASIC -G (which stands for your choiceof "Graphics" or "Games"). BASIC -I isa fairly decent BASIC, as such things go,but you need BASIC -G to get at all thecapabilities of the machine, which is whatthe proud owner of an M-5 will naturallywant to do. As far as we could tell,anything you could do in BASIC -I couldbe done just as well, if not better, inBASIC -G.

The two games, "Tank Battalion"and "Step Up" (a Donkey Kong variant),were mildly entertaining, but not as goodas they could have been with realjoysticks. The FALC spreadsheet wasfunctional if somewhat unwieldly.

Turning the machine around, youfind other connectors. There are two DINplugs, for the power and cassette inter-face, a 16 -pin connector marked"PRINTER", two joypad connectors,and RCA jacks for sound, video, and RF.Around the corner is a mysterious littleswitch, marked "H" and "L", that themanual doesn't mention.

Internally, the machine has a Z -80Aprocessor running at the nice even speed

of 3.579545 MHz. Well, why use twocrystals when one will do? There'snothing wrong with letting the wholemachine run at the speed of its video out-put. Some internal firmware is included,containing standard stuff that most, if notall, cartridges would need, and at leastone custom chip.

Basically BASICBASIC -G is a fairly powerful BASIC withlots of features. Among the most notableare sprites and interrupts. (More on theselater). The BASIC is quite easy to use,especially once you get used to all the nicelittle features (the editing and so on).

This BASIC is of the integer -onlypersuasion, which is good for its intendedpurpose of playing games, where speed iseverything, or almost everything, butdecidedly bad if you want to do scientificcalculations or anything involvingfloating-point numbers. The BASIC -Gmanual mentions something calledBASIC -F, which might be more usefulhere.

On power -up, the review machineclaimed to have 7067 bytes free, althoughthe technical literature mentions that 32Kof external RAM can be added. Thisalmost -8K is certainly enough for mostsimple BASIC programs.

One thing that you notice almost im-mediately is that this BASIC doesn't likeit when you concatenate two keywords.You can't say "PRINTA" or"IFB = CTHENGOTO592". You have toput in the spaces and say "PRINT A" or"IF B=C THEN GOT0592". When youlist your program, it will automatically in-sert all appropriate spaces for readability,lowercase BASIC keywords, and upper-case variables. Program listings look nicewith this computer.

One bug with the program listings isthat the LIST command, given a singleline number (LIST 400, for example), willlist from that line through to the end ofthe program. To list a single line, you haveto type in LIST 400,400.

You can redefine the character fontsif you wish. The command STCHR"EF8485C5858585F5" TO &45,1 will, forexample, change the capital E to aminiature ETI logo. You can have lots offun making the screen completely unread-able by changing all the characters. Thispales after a while.

You eventually discover that a stringvariable cannot hold more than 18characters. One supposes that this makeslife easier for the BASIC, and you usuallydon't need more. The more elaborate ap-plications that might need longer stringsare generally done on larger machineswith real keyboards and lots of disk spaceanyway.

AliensThe M-5 can generate some extremely

Sprites used in a video game.The large alien is composed offour sprites, connected usingthe JOINT statement.

The alien is hit, anddisintegrates in a mostsatisfactory manner. The in-dividual sprites are clearlyvisible.


respectable graphics. No less than 32sprites reside in the dark, if somewhatminiscule, interior of a TMS-9918A videodisplay chip, along with the other work-ings for high -resolution colour pictures.

The BASIC -G software providessuch tricks as drawing circles, boxes,bars (solid boxes), filling in areas(although the user is warned against fillingin donut -shaped areas, since this can ap-parently result in an infinite loop), and thelike.

The sprites are, however, the mainfeature of the graphics section. Individualsprites are little 8 by 8 bit beasties. TheSTCHR function is first used to redefine aconvenient character in the alternatecharacter set. One then uses the SCODand SCOL statements to set a sprite to acharacter code and to colour the spriterespectively. The LOC statement can thenbe used to pop the sprite up onto thescreen.

Moving sprites around is easy withthis BASIC. You tell the machine toMOVE a given sprite either to a certainpoint or in a given direction, at a givenspeed. The machine then moves the spriteas directed. The BASIC program can thengo off and do something else. Two impor-tant advantages arise from this fact, that aBASIC program does not need to movethe sprites itself. First, the program issimpler. Secondly, and more importantly,the program executes more quickly, sincethe heavy work is done in machine code.This is probably the single most importantfeature in making BASIC video games runquickly.

You can join four small sprites intoone big 16 x 16 bit sprite. You can alsodouble the size of the sprites. You canthus create really large sprites that blowup very realistically (just like the rocks inAsteroids) when hit, by having the com-ponent sprites fly off in random direc-tions. This can keep the kids thrilled forhours.

100 GOTO 100One of the most notable features of theM-5 is its interrupt -driven BASIC. What,you may ask, is an interrupt? Well, an in-

terrupt is an event, either in software orhardware, that causes the computer to setaside whatever it's doing at the moment,go do something in response to that event,and then return to its original task. TheM-5 provides six different interrupts: ER-ROR (whenever it hits a BASIC error),EVENT (a timer that can be set to providean interrupt every second or so), ALARM(at a given time on the M -5's hours -and -minutes clock), COINC (two sprites col-liding), JOY (any movement of thejoypads), and KEY (any keyboard key, orthe joypad fire buttons being depressed).

To use an interrupt, you give thecomputer a command like ON COINCGOSUB 1000, followed by COINC ON toenable the thing. Your program can thenmeander merrily along, happily flingingsprites across the screen at each other.Whenever two sprites manage to impalethemselves on each other, the subroutineat line 1000 will be called. This routine canthen sort out the debris. Add interruptroutines for EVENT (let the aliens changedirection and drop bombs twice a second),JOY (so you can fly around), and KEY(so you can blaze away at them with yourlaser cannons), and you have a completevideo game. The main part of the pro-gram simply sets everything up and thendoes nothing: 100 GOTO 100. Whenveranything happens, it wakes up, handles it,and goes back into its infinite loop.

Two complaints about the interruptcapabilities: First, on a COINC Interrupt,it is difficult to tell immediately exactlywhat hit what. There is a function,COINC(X), that tells you what, ifanything, sprite X hit, but there shouldreally be a better way. Second, thereshould be an interrupt on MOVE com-pleted, such that you could then causewhatever had been moving to dosomething else.

These features, the sprites and the in-terrupts, make the BASIC ideal for pro-gramming games in. Your program pro-vides only the control functions - whatthe screen should look like, what movesaround and how, and what happens whenthings collide - and BASIC handles thereal work in its machine code. The result,since so little is done at the speed (or lackthereof) of BASIC, is that games act as ifthey were written in asembler, without theassociated programming headaches. You

can write decent video games without be-ing a programming genius.

Sounding OffAlso included in the M -5's internals is anSN76489AN sound generator chip. Thiscan produce all kinds of weird and not soweird sounds. For example, the commandPLAY "EAO6E" causes the first bar of"Lucy in the Sky with Diamonds" to beplayed. You can change the tempo, thevolume, the type of sound, and so on. ThePLAY command can be made to play har-monies, by giving it three things to play atonce. Sharps, flats, triplets, octaves, dot-ted notes, rests, and staccato are included.

Should your musical tastes be lessconventional, you can access the soundgenerator directly. There are four chan-nels, three of which produce tones. Thefourth produces noise (explosions, etc.).Everything needed to produce the soundeffects for your video games is here.

On the other hand, a really high browvideo game would be done completelywithout sound effects. To be technicallyaccurate, it would have to reflect the reali-ty that sound doesn't travel through thevacuum of space. Besides, it's really neatto be able to kill in silence.

Moving UpBeyond the games and graphics that themachine is so good at, there seems to belittle room for expansion. One glaringomission that the experienced program-mer will notice immediately is that thereappears to be no provision for a disk in-terface. Such an interface might possiblybe made through the cartridge connector,though. The technical manual mentions aserial interface that can be connectedhere, but absolutely no mention of a diskcontroller is made. Without disks, youcan save programs only on cassette, whichlimits both what you can do and howeager you will be to do it. The FALCspreadsheet cartridge, for example, isrendered nearly useless by the lack of adisk.

A printer output is provided. Al-though we have not seen the printer that issupposed to go here, its capabilities sup-posedly include reproduction of graphicsfrom the screen.

ConclusionsThe one thing that the M-5 does excep-tionally well is to program games inBASIC. Its capabilities here make it an ex-tremely worthwhile machine, if you'rewilling to pay the price. If, on the otherhand, you're into serious data processing,and you want to save your programs on adisk at the end of the day, $460 could go along ways toward buying a clone. TheSord M-5 is a computer for people whowant a cute little machine to have lots offun with.


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1

II

Designer's NotebookWho needs to bother win-ding miles of wire onto abobbin when highvoltages can be generatedwith some inverters and ahandful of diodes andcapacitors? Rory Holmesshows how it's done.IN THIS MONTH'S Designer'sNotebook we shall be looking at a varietyof interesting voltage multiplier circuitsthat can be built using ordinary CMOSgates and common -or -garden 1N4148signal diodes. DC -to -DC converters for anumber of applications became possibleby simply driving voltage multiplier chainswith an AC clock signal, again im-plemented with CMOS gates. The initialsupply voltage can be multiplied bothpositively and negatively to give, for ex-ample, a split rail op -amp supply from astandard 5 V TTI supply. Negative andpositive voltage references used inanalogue -to -digital conversion and othersignal conditioning circuits can also begenerated, as can general purpose highvoltage bias rails.

By using a novel 'chain' of invertergates to independently drive each node ofa diode -capacitor ladder, some ratherunique circuits result.

Chain ReactionFirst, let's look at the usual multiplier cir-cuits shown in Fig. la. These are normallyused with rectifier -type diodes, low fre-quency AC inputs (sine waves) fromtransformers, and electrolytic smoothingcapacitors. At first glance there seems tobe no common pattern between them, andlittle similarity to the multiplier chains us-ed in TVs and other high voltage powersupplies.

However, in all cases the AC inputwaveform is fed via capacitors to appearat those circuit junctions marked 'A' inFig. la, while those junctions marked 'D'will maintain a steady DC potentialrelative to the ground point. We can thusredraw the circuits by connecting up thecapacitors in two series chains (assumingtheir values are altered accordingly) andstill preserve the same circuit action. Onechain carries the AC signal, while theother accumulates the DC voltage shifts.Figure lb shows these redrawn circuits,which now appear as extensions of the

standard ladder network. The doubler, ofcourse, remains in its original form since itonly has one set of capacitors.

Fig. 1. Standard voltage multiplier circuits.

Starting with the doubler, we canbuild a very simple DC -to -DC converterin one CMOS gate as shown in Fig. 2. TheSchmitt inverter gate is configured as asquare wave oscillator running at about100 kHz - the multiplier capacitors C2and C3 will therefore have a low im-pedance at this frequency, which is alsowithin the switching speed capability ofthe 1N4148s. For this reason, rectifierdiodes such as the 1N4001, which havemuch slower switching speeds, cannot beused in these circuits.

Fig. 2. A CMOS doubler circuit.

The oscillator output at point 'A' willtherefore be switching between the 0 Vand 10 V supply levels. When the output isat logic low, capacitor C2 will charge uppositively (in the direction of the arrow)via DI. D2 is reverse biased and so effec-tively out of circuit. When point 'A' goeshigh to + 10 V, the positive end of C2 at'B' will be raised to + 20 V. This reverse

biases DI and allows C3 to charge upthrough D2. The voltage on C3 is thusmaintained at about + 20 V less two diodedrops (i.e., at 18V6) as the cycle repeatsitself. This is known as a diode chargepump.

Building An ExtensionThis principle can be extended using ex-actly the same chainlike structure as il-lustrated in the positive and negativemultipliers of Fig. 3. In both cases the in-verter gates are cascaded and driven froma square wave oscillator at around 100kHz. Each inverter gate contributes itsown output current (a maximum ofaround 2 mA) via the capacitors into themultiplier chain; because of this, theavailable output current will always be thesame no matter how many times thevoltage is multiplied (two times in thiscase).

The positive multiplier output of Fig.3a includes the initial positive supplypotential, and so generates three times thisvoltage less the three diode drops of OV7each. The negative multiplier of Fig. 3b,on the other hand, is referenced to theround rail, given -2 times the voltage(again less the diode drops).

As mentioned before, all the diodesare 1N4148s; the multiplier capacitorsC2-4 are all non -critical and may beanything from lOnF to 100nF. C4 may be

0

0no

VEOUTPUT

VOLTAGE

NOTEALL 010EMS ARE 11.11C=A ARE lOn 10. CERAMICALL GATES ARE ANT 8 SERIFSCMOS INVERTER

Fig. 3a. A two -stage positive voltage multiplier(multiplies by +3). b. A two -stage negativevoltage multiplier (multiplies by -2).


Designer's Notebook

a polarised tantalum capacitor of a fewmicrofarads to provide furthersmoothing. Any type of CMOS gatewhich can be connected as an invertercould be used, as well as all the standardinverters, though the 4049B hex inverteroffers slightly more output current. It'salso possible to use the 74C series typessuch as the 74C04 or 74C14. Pin -outs forthese chips are given in Fig. 4 and not onany of the circuit diagrams, since they dif-fer from type to type.

Fig. 4. Pin -outs for the standard hex inverterpackages which may be used in the circuitsgiven in this article.

The oscillator implementation and itsfrequency are also non -critical; you couldexperiment with anything from severalkilohertz to several hundred kilohertz.Remember, though, that as the frequencydecreases, the impedance for a givencapacitor value will increase, so increasingthe impedance of the multiplier output.

Table 1 lists out the different voltagesyou can expect from different chainlengths and supply voltages, based on thecircuits of Fig. 3. The number of stagesrefers to the number of capacitors that areactively driven from inverter outputs. Us-ing this table it becomes very easy todesign a generator for any voltage require-ment; the output voltage could beclamped to the exact level required usingan ordinary zener diode regulator. Butremember there isn't much currentavailable, and as the output is loaded, thevoltage will decrease due to the supply im-pedance. The higher supply voltages willgenerally provide more output current.

As an example, Fig. 5 shows a longermultiplier designed to give 110 V and builtusing only one hex inverter IC of theSchmitt trigger type (40106B). Usingceramic capacitors, this circuit could bebuilt to a very small size.

Operating PrinciplesHow do these multipliers actually work -the doubler circuit of Fig. 2 is straightfor-ward, but what about the longer types?Voltage multiplier explanations are usual-ly notoriously difficult to follow, let aloneunderstand, and we shall therefore adopt

a more graphic approach. If we measurethe voltages at the lettered points in Fig.3a and plot them against time, we get thewaveforms shown in Fig. 6. These wave-forms have been idealized for clarity - noaccount has been taken of the voltage

ISV SUPPLYVOALTGE0/0.01

NOTEUSE 4010611 OR 74G14 FOR INVERTERSC2 CS ARE 22n 42n CERAMIC

OV

O TAOEAiT SmA

Fig. 5. A 110 V supply using one hex inverterIC.

drops due to the diodes in the circuit.From these it can be seen that the voltageacross C2 (the difference between thewaveforms A and B) is a constant IV,where V is the supply voltage, while thatacross capacitor C3 (between points C andD) is 2V. We also know that the final out-put voltage across C4 is 3V. Moving downthe chain towards the final output, then,we find that each capacitor maintains aDC charge which increases in integermultiples of the supply voltage. How so?

Consider capacitor C2 in Fig. 3a. Atpower -on it is discharged, but when pointA switches low, it charges up to the supplyvoltage via DI (neglecting diode drops).Point B is therefore at supply voltage.When point A switches high, then, pointB is raised to twice the supply voltage.Point C must be at zero volts since it is theinverse of point A, so current flows via D2(which is now forward biased) from pointB into C3 until C3 is charged up to thevoltage at B (i.e., twice supply). The nextclock pulse takes point A low, so point Bis at supply less the voltage that has leakedinto C3, and C2 is topped up via DIagain. Meanwhile point C has switched tosupply voltage, so point D is now at threetimes supply and D2 is reverse biased,preventing C3 from discharging back intoC2. C3 can discharge into C4 via D3,however, so the the voltage across C4 ismaintained at three times supply.

It should now be clear that no matterwhat the length of the multiplier, eachcapacitor in the chain maintains a steady

Fig. 6. Waveforms for a two -stage positivemultiplier (idealized for clarity with diodedrops ignored).

DC charge which equals that on theprevious one plus the supply voltage, andeach capacitor tops up the next one in thechain on each alternate half -cycle. Figure7a, for example, shows five stages of amultiplier chain driven by a square wavesignal, while Figs. 7b and 7c use awaveform to represent the voltage levels ateach capacitor node for each half of thecycle. The direction and voltage of the DCcharges on each capacitor is also shown -remember these are constant as shown bythe graph of Fig. 6.

Fig. 7. How multiplier voltages accumulatedown the chain.

Looking at Cl and C2 in Fig. 7b wecan see that the positive (top) end of Clwill be at V volts (V is the supply voltage)while the positive end of C2 is at 3V volts(2V of its own, raised up a further V voltsat the CMOS output). Diode D2 willtherefore be reversed biased and effective-ly out of circuit. For similar reasons C3will be at 3V volts (less that which hasleaked away) and can therefore be charg-ed up via D3 from C2. On the other halfcycle in Fig. 7c, however, C3 will be raisedup to 4V volts by the CMOS output, whileC2 returns to 2V. So this time D3 isreverse biased and will not conduct. Cl isnow raised to 2V and can thus charge C2via D2. The conducting and non -conduc-ting parts of the circuit for each half cycleare shown in Fig. 8, which gives a muchclearer illustration of the diode chargepump action.

The Appliance of ScienceFigure 9 shows the circuit of a split -railpower supply that generates ± 10V from a5V supply input. It could be used to power


TABLE 1CMOS SUPPLY VOLTAGE

5V 101/ 18V

\ OUTPUT POLARITY + - + - + -NO. OF STAGES \

1 8.6 3.6 18.6 8.6 34.6 16.62 12.9 7.9 27.9 17.9 51.9 33.93 17.2 12.2 37.2 27.2 69.2 51.24 21.5 16.5 46.5 36.5 86.5 68.55 25.8 20.8 55.8 45.8 103.8 85.86 30.1 25.1 65.1 55.1 121.1 103.17 34.4 29.4 74.4 64.4 138.4 120.4

Table relating supply voltage and number of stages to the (unloaded) output voltage, for positive andnegative output multipliers based on the circuits of Figs. 3a and 3b and allowing OV7 for each diode drop.

low current op -amp circuitry and otherCMOS circuits from a standard TTLpower supply. Again, only one hex in-verter pack is required and we recommendthat the 4049B is used with its slightlyhigher output current capability. The cir-cuit takes advantage of the three cascadedinverters that drive the positive multiplierchain, by also using them to form a 'ring -of -three' oscillator. The multiplier chain istherefore self -oscillating!

The positive side in turn drives thenegative chain of ICld,e and f. FromTable 1 we would expect the available out -

CLOCKNIGH

CLOCKLOW

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CLOS OUTPUT DRIVE LEVELS

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COS PUT DRIVE LEVELS

put voltages to be + 17V2 and -12V2,which are then clamped to the ± 10 Vlevels by zeners ZD1 and ZD2. Serieslimiting resistors for the zener diodes areunnecessary due to the current -limitedoutput of the multiplier.

Fig. 8. Charging paths for an extendedmultiplier chain. The diagrams only show thosediodes which are forward biased (conducting)during alternate half cycles of the drivewaveform.

11111111111111111111111111111111111111111111111111111111111111111111111 1111111111111111111111111111111111111111111111111I 111111 I lin

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Designer's Notebook

It> It> lo It* It*C7 C8 C9 C10 C11

+18V

-18V0. D1

PP39V

PP39V

D2 03 D4 175

NOTE:IC1.4 ARE 40106B OR 40498D1-25 ARE 1N4148C1.6 ARE 22-68n 100V CERAMICC7-12 ARE 22-68n 250V CERAMICC13-18 ARE 22n -68n 350V CERAMICC19-25 ARE 22-68n 500V CERAMIC

D6

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D7 D8 D9 D10 D11 D12

+18V

It* Ittt it* it* It'C13 C14 C15 C16

D13 D14 D15 D16 D17 018

It> 1> It* I> It>019

C20

D20

C21

D21

C22

D22

C23

D23

+18V

D24

C12

1207V)

C18

(311V1

C24

D25

011 0+433V+.C25

Fig. 11. A 433 V generator using a 24 -stage positive multiplier and an 18 V supply.

OV

iaTANTALUM

g.TANTALUM

DE D7 D.

ISICI

TI 40498 OR 74004

D19 ARE IPPON.

MA:IRMA. !OTT TAILCERAMIC OR POLECARBONAT.

OUTPUT CURRENTS ARE In. FOR 74004lun FOR 404.0

IOV

Fig. 9. A split -rail supply using one hex inverterpackage.

Figure 10 shows a variation on theprevious circuit's positive multiplier sec-tion, using all six inverters to providemore output current at ± 10 V. To achievehigher output currents, simply parallel theCMOS gates that drive the capacitorchain; the available currents will addtogether due to the nature of the CMOSoutput FETs. This technique is useful forCMOS operating at low supply voltages.

Figure 11 gives the circuit for a24 -stage positive multiplier to generate ahigh -voltage, low -current supply. Thiscould be used for a solid state `megger'(high resistance meter and insulation

tester). The 24 stages can be achieved us-ing only four hex inverter packs, and willprovide 433 V from an 18 V supply. Thiscircuit illustrates the fact that the invertersmay be wired up in any fashion so long asalternate capacitors receive oppositephases of the square wave.

The circuit will deliver at least 2 mAat 430 V! - not lethal but pretty painful,so be careful. We suggest the addition of aIMO series resistor in the positive supplylead to limit the available current to about40 uA. A 100 uA meter would providesuitable megaohm readings.

Fig. 10. Paralleling inverter stages to give ahigher current supply.

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Nuclear Applicationsin Archaeology

One of a pair of 300 pairs of rope sandalsfound in an Eastern Oregon cave. Carbondating revealed that they are about 9000 yearsold.

Photo Courtest of William F. Libby

The different scimethods of analysisthe archaeologist and the

historian to uncover awealth of facts from

samples.

by Roger Allan

CUSTOMARILY, LAYMEN'Sknowledge of the application of nucleartechniques to archaeology can be summedup with a single method: the dating pro-cess via Carbon-14. It is well known, earn-ing the Nobel Prize in 1960, for itsdiscoverer, Willard F. Libby. Its ripple ef-fect on the study of Archaeology is incom-parable, oftentimes related to thediscovery of the periodicity of elements inthe field of chemistry. But it is only one ofa number of such nuclear applications,and while being the first, foremost andmost generally useful of such techniques,cannot answer a number of questionsabout artifacts which Archaeologists needto know. It has its drawbacks. Its primaryuse is in the dating of wood and vegetable

matter, with increasing difficulty in usefor the dating of bone, textiles, ivory andiron (iron can in some circumstances bedated using this method because ironfrom very old samples contains carbonderived from wood charcoal).

A quick overview of the theory andprocess: The earth is being constantlybombarded with cosmic radiation, oneform of which is neutrons. These reactwith nitrogen in the upper atmosphere toproduce carbon-14. The flux of suchneutron bombardment has been constantthroughout history, up until about 1900when man commenced to disturb thenatural environment and unbalanced thecarbon-14 constancy of uptake. Thiscarbon-14 reacts in the atmosphere to

form carbon dioxide. The carbon dioxideis taken up by all forms of vegetation, andhence into all life forms that eat vegeta-tion. The amount of uptake ceases at theconclusion of the animal or plant's life,resulting in a set amount of carbon-14 inthe artifact. Carbon-14 has a half life of5730 years. By taking a sample of the ar-tifact, one can measure the amount of re-maining carbon-14, and hence date the ar-tifact. (The word "artifact" properlymeans a man-made object, but is often us-ed to mean any object under ar-chaeological examination.)

There are a number of ways of ac-tually doing the dating process. Libby in-itially used a process called a "screenwall" counter, basically a form of geiger


counter. There are two major processesused today, the gas proportional counterand the liquid scintillation counter. Thedecision as to which process to use isdependent largely on the size of the sam-ple to be tested; the gas proportionalcounter can use small samples while the li-quid scintillation counter can handle largesamples, but not vice versa.

Gas ProportionalIn the gas proportional process, a finewire, charged to a high voltage, is strungdown the center of a metal tube. The sam-ple is introduced in the form of a gas pro-duced from the carbon in the sample.When carbon-14 decays, the radiation itemits produces free electrons in the gas,which are collected by the wire where anelectrical impulse is generated. This iscounted and the number of impulses, ex-pressed as disintegrations per minute(dpm). A fresh sample, that is, one thathas recently died, will have a dpm rate of15, one 5730 years old a dpm of 7.5 and soon. It is accurate up to about 50,000years.

The difficulty with this system is theamount of background radiation affec-ting the counter while the sample is beingtested. The overcome this, an anticoin-cidence counter is arranged such that if itregisters a disintegration at the same timeas the counter registers a disintegration,the disintegration is automatically dis-counted. This is because the disintegrationregistered by both counters could onlyhave occurred by some external radiationsource, and not from the sample beingtested. The disadvantage to this system isthat it must be made quite large to accom-modate a large sample, since the gas is of arelatively low density. when the counterbecomes large, the background rate goesup, the shielding and anticoincidencecounter become still larger, and the ad-vantages are generally outweighed by thedisadvantage of size.

Liquid ScintillationA second method to test for carbon-14 isthe liquid scintillation counter system.The carbon in the sample is converted intoan organic liquid such as benzene. Otherchemicals, added to the benzene, emitflashes of light (scintillations) when radia-tion passes through them. The solution isplaced in a glass bottle and monitoredwith photomultipliers which convert thescintillations into electrical impulseswhich can be counted. The difficulty withthis system is that low backgrounds can-not be obtained because of the minimumamount of electrical noise in this type ofsystem. However, for large samples, thisdisadvantage is overcome because the li-quid is relatively dense.

There are a number of other similar

A terra-cotta statuette originally thought to beof Etruscan origin between 510 and 490 BC.

Thermoluminescence dating disclosed that thestatue was a fake of modern origin. Photos

courtesy of Stuart Fleming ResearchLaboratory for Archaeology.

Electronics in Archaeology

such processes, involving the half-lives ofradioactive potassium -argon -40 (used todate Zinjanthropus, the "human" skullfound in 1959 at Olduvai Gorge by Dr.Leakey), rubidiumstrontium, lead -204and some twenty others. Each has anespecial, limited use and a writer on thissubject quickly gets into the grey area bet-ween Archaeology and the dating ofgeological formations.

One of the most common artifactsfound at an archaeological dig are pot-sherds, the remnants of broken pottery. Amethod for dating them, originally deriv-ed at Oxford University, involves ther-moluminescence.

ThermoluminescenceThe method itself is based on the principlethat radiation distorts the electronic struc-ture of insulating materials and so storesenergy within the material. This processmay be likened to the stretching of a spr-ing. When the material is heated to a cer-tain temperature, the forces holding theelectrons "out of place" begin to"loosen", the structure relaxes as a stret-ched spring would and the stored energy isreleased. The released energy is emitted inthe form of light. The radiation that pro-duces this deformation comes mainlyfrom naturally occurring radioactivematerials like uranium, thorium andpotassium which are present in the potteryin low concentrations. The soil in whichthe pottery was buried also containsnaturally radioactive material which af-fects the pottery in the same way. Cosmicradiation also contributes to the radiationdamage. As time passes, the pottery ab-sorbs more and more radiation, startingfrom the last time the pottery released itsstored energy, that is, when it was anneal-ed (baked or fired).

By carefully powdering a sample,taking care not to heat it (so that the ther-moluminescence is not inadvertantlyreleased), and then gently heating it in aprecisely controlled oven, the release oflight can be detected by photomultipliersand recorded. Then the examiner must

deduct the amount of thermoluminescnceexpected to have been absorbed by thesample from the surrounding soil since thelast time it was annealed, and further,deduct the amount of cosmic ray uptake.When all the arithmetic has been done,then a fairly accurate reading can be ob-tained as to the sample's age. Not onlypotsherds, but ceramic and terra-cottastatuary can be analyzed this way,resulting, on occasion, in the finding offorgeries. Its major disadvantage is that itis destructive.

A second method utilizing radiationdamage was developed in the early Sixtiesand is called fission -track studies.

Tracking UraniumEssentially, uranium -238 occasionallysplits into two parts, similar to the reac-tion in a nuclear reactor. It does not,however, happen very often; only 84spontaneous emissions occur per millionatoms per million years.

When the fission occurs in a piece ofpottery, the two parts of the split atomleave a tiny trail of damage in the crystalstructure of the material. If this happensclose to the surface of the specimen, thetrail will penetrate the surface and can bedetected.

The detection process consists of tak-ing a tiny slice of the specimen (as small asa square millimeter) which is then cleanedand polished. An acidic solution is thenapplied to the surface. This attacks thespecimen and eats away at its surface. Thetracks of the fission become enlarged tosuch an extent that they can then beobserved with an ordinary microscope. Bycounting these holes, or etch pits, in aknown area, one obtains the number offissions that occurred in that area sincethe pottery was annealed.

The second step in the dating processis to determine how much uranium is pre-sent in the area where the tracks werecounted. By irradiating the specimen witha known quantity of neutrons, one cancause the uranium -235 atoms to fission.

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Toamplifier

ohms

Essential parts of a mass spectrometer. Atoms to be analyzed are changed to ions in the source.Then the ions are accelerated by high voltage, deflected in a magnetic field according to theirmass, and the intensity of the separated beams is measured in the collector.

Because the uranium -235 is customarilyconsidered to be in a fixed proportion tothe uranium -235 (though see OKLO, ETI,July, 1983), the number of new fissiontracks in the area previously observed is ameasure of the amount of uranium -238 inthat area and may be easily calculated.

The accuracy of this method isdependent on the amount of uraniumfound in the clay from which the potterywas made, customarily 1 part per million.Such a concentration permits the deter-mination of ages as recent as 100,000years with an uncertainty of 10%. However,as the concentration of uranium goes upto, say, 100 parts per million, ages as re-cent as 1,000 years can be determined.With a concentration of 1%, ages as recentas 10 years can be determined. Further,glass, which has had uranium deliberatelyadded as a coloring agent, can have its agedetermined by this method.

Fingerprints and NeutronsFingerprinting, that is, the determinationof trace elements (less than 0.01%), is anon-destructive way of measuring verysmall quantities of elements such thatsimilarities and differences can be deter-mined, which in turn permit a betterunderstanding of archaeologicaleconomics.

While trace elements can be deter-mined by ordinary chemical methods largesamples would be required that might ruinvaluable objects. The main form offingerprinting, the neutron activation pro-cess (NAA), has the great advantage thatit is non-destructive. Analysis by means ofthis method (outlined in more detail inART, ETI, July, 1983) consists of bom-barding the atoms of a element in a sam-ple with neutrons in a reactor. This causessome of the atoms to absorb a neutron. Inmost cases, this will result in some frac-tion of these atoms becoming radioactive.


For example, sodium: when bombardedby slow neutrons, the sodium absorbs aneutron to become a sodium nucleus with12 rather than 11 neutrons (sodium -24).This decays to a magnesium atom, emit-ting a beta particle and energy in the formof gamma rays. the number and energy ofthe gamma rays is unique for the decay ofsodium -24 and thus constitutes a kind ofsignature. Further, measuring the half-lifeof sodium -24 is also a means of identifica-tion. In other words, by this method onecan determine that sodium is present bylater observing the energies of gamma raysfrom sodium -24 and can determine howmuch is present by measuring how manysuch gamma rays are emitted. The sen-sitivity of this process is very good, withgold being capable of being detected inquantities as small as a millionth of onemillionth of a gram (one picogram).

An example of the use of the NAAprocess involved determining the sourceof material for Indian arrowheads madeof obsidian. At the University ofMichigan, Adon A. Gordus was able topinpoint the material used by theHopewell Indians, a group that inhabitedwhat is now Ohio, Illinois, Michigan andWisconsin during the period 300 BC to500 AD.

The puzzle was that while obsidianarrowheads were found in Hopewellburial mounds, the closest sources of thatmaterial are in the Western U.S., Mexicoand Alaska.

Using NAA, Gordus analysed the ar-rowheads and the obsidian from all theNorth American sources for twoelements, sodium and manganese. Hefound that only three sources containedthese two elements in concentrationssimilar to those of the arrowheads. Hethen used NAA to check for 15 otherelements in these sources and found thatonly the composition of obsidian fromone source, Obsidian Cliff in Wyoming's

Yellowstone National Park, correspondedto the composition of the arrowheads. Ar-chaeologically, this means that there wassome sort of trade route between the twoareas.

A second example of NAA is morerecent. Early photographic plates tend tobecome blanched with age, such that thepicture can no longer be seen. However,by irridating the plate with slow neutrons,and then placing a photographic film incontact with the plate, the gamma decaywill effect the modern photographic plate,permitting an image of the previously"unseeable" picture to become apparent.

Carbon-14 dating is onlyone of a number of nuclearapplications which answer

questions aboutarchaeological finds.

One specific example of this is the 19thcentury picture currently in the Smithso-nian Institution, taken by the English an-tiquarian, physicist and pioneer in opticsand photography, William Henry FoxTalbot. Talbot's plate is now blank, butunder NAA reveals the original picture, atable setting.

Sparks and SpectrumsA second form of fingerprinting involvesspark source mass spectrometry. In thismethod, a sample from an artifact is sub-jected to a very hot, electrically producedspark. A small part of the specimen,usually metal, is vaporized and the in-dividual atoms become electrically charg-ed or ionized. This process takes place atone end of a curved metal tube that hasbeen evacuated to a low pressure. Themetallic ions are then accelerated in anelectrical field of about 1000-2000 volts in

(Upper photo) Afaded photographicplate by photopioneer WilliamHenry Talbot. (Farleft) Using theneutron activationprocess, the originalphoto scene isrestored. Bothphotos courtesy ofthe Smithsonian In-stitution.

such a way that a narrow beam of ionstravel down the tube.

At the point where the tube bends,there is a magnetic field that bends thepath of the ions. The important point isthat the amount that the path of an ionbends is determined in part by its mass.The arrangement produces a separation ofions into numerous beams according totheir mass. The beams eventually strike aphotographic plate that upon beingdeveloped, shows a series of lines cor-responding in position to the masses ofthe ions which struck the plate. The inten-sity or blackness of each line is a functionof the concentration of the element at thatmass number. By comparing suchphotographs from different sources, anddifferent finished products, the ar-chaeologist can determine ancient tradepatterns, eg. equating a coin minted inRome with a gold mine in Spain, for in-stance.

Lead IsotopesA third type of fingerprinting used by ar-chaeologists involves lead isotope ratios.The metal lead has been used by man inone form or another for thousands ofyears. It is obviously present in thingsmade mainly of lead, but is also a minorconstituent of many alloys, includingbronze and brass. In addition, glazes con-taining lead have been used in pottery,and glass sometimes is colored by havinglead compounds added to it.

The fingerprint for lead is the relativeamounts of the four stable (non-radioactive) isotopes of lead found innature: lead -204, -206, -207 and -208. Theratios of the lead isotopes in any givenlead ore deposit were initially determinedby the timing of the geological event thattook place when the deposit was beingformed.

The relative amounts of the isotopesin a sample can be determined with a mass


Electronics in Archaeology

spectrometer similar to the one detailedabove. However, only the four isotopes oflead and their ratios are of interest. Thefour separated beams which are obtainedbombard the metal plate one at a time. Byslightly varying the beam acceleratingvoltage to focus each mass on the plate insuccession, the number of ions of eachmass striking the plate can be measuredwith a device called an electrometer. Ac-curacy is within 1%.

The main disadvantage in studyinglead isotopes and their ratios is that theseratios are not unique to any given leadmine. However, the method can be usedto prove that the lead in an object did notcome from a particular place. When thisinformation is used in conjunction withother information (trace element patterns,perhaps) it can be quite useful inestablishing the ultimate source ofmaterial, and indirectly, the trading habitsof the peoples who created them. For ex-ample, Swiss workers were able to tracethe sources of lead used in Roman waterpiping to various ancient lead mines inEngland, Spain and Central Europe.

Beta BackscatterEnergetic electrons, better known as betarays, are another tool used in ar-chaeological studies. Emitted by manyradioactive atoms, beta rays striking a sur-

face are either absorbed or penetrated alittle way and are bounced back (backscat-tered). Elements having a higher atomicnumber are more efficient backscatterers.

This process has been used as a non-destructive means of measuring theamount of lead in leaded glass and in pot-tery that has been finished with a leadglaze. Essentially, a beta ray emittingradioisotope is allowed to shine on thesurface being analyzed and a geigercounter measures the beta rays that arereflected. The more lead there is in thesurface, the more scattered radiation ismeasured by the counter. An example ofits use was in the study of the famousEnglish crystal glass known asRavenscroft, produced towards the end ofthe 17th century. Analysis of pieces fromthat time and from a century later showedthat the amount of lead used was increas-ed as time when on.

One of the more interesting applica-tions of nuclear processes to the study ofarchaeology involves the Mossbauer Ef-fect, first determined in the late 1950s byRudolf Mossbauer. He then discoveredthe key to a method in which the nuclearproperties of certain elements can be af-fected by their chemical and physical cir-cumstances. While relatively few elementscan be studied by this means, iron hap-pens to be the easiest, which is ar-

chaeologically fortunate, since iron com-pounds, especially oxides, have been usedto add color to pottery for thousands ofyears.

Resonance AbsorptionIn the case of iron, one begins with aspecially prepared radioactive source con-taining cobalt -57. The radiation from thissource is allowed to pass through a thinlayer of the sample and then falls upon adetector where the amount of radiation ismeasured. While part of any radiation isabsorbed when passing through anymaterial, some of the radiation from thecobalt -57 source is very special, ar-chaeologically.

This special radiation, which consistsof gamma rays with an energy of about 14keV, tends to be preferentially absorbedby the nuclei of iron -57 atoms because it isexactly the right energy; in other words,the iron -57 is resonance -absorptive. Theexactness is important, as the slightestalteration will destroy the resonance ab-sorption.

Utilizing the Mossbauer effect, thescientist moves the radioactive source atvarious velocities back and forth andmeasures the radioactivity reaching thedetector at each one. If the iron in thesample is at a particular state, dependentupon its heat when being annealed, a state

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ETI ORDER FORMwhich is different from the iron atoms in the decaying source,then a certain velocity will exactly compensate for the differenceand restore the resonance absorption.

A graph showing the measured radioactivity at each of manyvelocities is called a Mossbauer effect spectrum, and will showone or more dips in it depending on how many and what kinds ofiron compounds are present.

An example of its use is in the study of medieval English pot-tery. Researchers found that they could estimate the firingtemperature of the pottery as well as tell the difference betweenpottery that was similar in appearance but from different sources.It is believed that this technique will eventually permit ar-chaeologists to reconstruct some of the ancient practices such thatthey will know more about the technology of the people whomade the pottery.

Occasionally, one-shot nuclear applications to archaeologyare required. An example is the study of the Second Pyramid ofChephren in Egypt. This pyramid, which is; about the same size asthe Great Pyramid of _Cheops, did not have as complex an inter-nal structure as Cheops. In the latter, a hidden upper chamberwas discovered in the 19th century, 3,400 years after its construc-tion. But in Chephren's pyramid, there is only one knownchamber, and archaeologists had wondered if there existed a se-cond, hidden chamber.

In 1960 a group from the University of California determinedto answer once and for all if such a second chamber existed. Theyused the highly penetrating components of cosmic rays known asmuons. Essentially, they tried to produce an X-ray picture of thepyramid. To do this a detection system was placed in the chamberlocated under the centre of the base of the pyramid. The detectionsystem consisted of spark chambers and scintillation counters thatenabled the group not only to detect the arrival of a muon but totell exactly from the direction it came. Some 700,000 muons weredetected and encoded on magnetic tape that was later fed into acomputer.

The computer turned the process inside out. By pretendingthat the detector was the source of the muons, and by tracing eachone back to an imaginary plane above the pyramid (analogous toan X-ray film), the computer was able to build up a picture onthat plane. The greater the number of muons coming from a givenpoint on the plane, the less stone they pass through on the way in-to the detector from that point.

The resulting picture, corrected for various geometric factorsin the detector construction and location, clearly showed the fourcorners of the pyramid. The computer was also able to see thelimestone cap that covers the point of the pyramid. Lastly, thestudy demonstrated once and for all that no secret or hiddenchamber exists in this pyramid.

Essentially, then, the applications of nuclear technology tothe study of archaeology are numerous. One can determine wheresomething comes from (NAA) and where something does notcome from (lead isotope ratios); its age (carbon-14), how it wasmade (Mossbauer effect), whether or not something exists(muons), and whether it got from point a to point b (spark sourcemass spectrometry). While certainly archaeology is as much art asit is science, the application of nuclear science provides a numberof tools for the archaeologist to get on with the art portion of hiswork.

CM

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ElectronicsELECTRONICS

BEGINNERSPH255: COMPLETE GUIDE TO READING SCHEMATICDIAGRAMS, 2nd EditionJ. DOUGLAS -YOUNG $10.45Packed with scores of easy -to -understand diagrams and in-valuable troubleshooting tips as well as a circuit finder chartand a new section on logic circuits.

PH251: BEGINNER'S HANDBOOK OF IC PROJECTSD. HEISERMAN $17.45Welcome to the world of integrated circuit (IC) electronicprojects This book contains over 100 projects (each in-cluding a schematic diagram, parts list, and descriptivenotes)

PH252: DIGITAL ICs: HOW THEY WORK AND HOWTO USE THEMA. BARBER $11.45The dozens of illustrations included in this essentialreference book will help explain time -saving test procedures,interpreting values, performing voltage measurements, andmuch morel

PH249: THE BEGINNER'S HANDBOOK OF ELECTRONICSG. OLSEN & M. MIMS,111 $11.45In this basic book, the authors cover the entire spectrum ofmodern electronics, including the use of such components asintegrated circuits and semiconductor devices in recordplayers, radio receivers, airplane guidance systems, andmany others.

THE BEGINNER'S HANDBOOK OF ELECTRONICSAB003 $11.45An excellent textbook for those interested in the fundamen-tals of Electronics. This book covers all major aspects ofpower supplies, amplifiers, oscillators, radio, television andmore

ELECTRONICTHEORY

ELEMENTS OF ELECTRONICS - AN ON -GOING SERIESF.A. WILSON, C.G.I.A., C.Eng.,BP62: BOOK 1. The Simple Electronic Circuit

and Components $8.95BP63: BOOK 2. Alternating Current

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And Circuits $12.30BM: BOOK S. Communication $12.30The aim of this series of books can be stated quite simply -it is to provide an inexpensive introduction to modern elec-tronics so that the reader will start on the right road bythoroughly understanding the fundamental principles involv-ed

Although written especially for readers with no morethan ordinary arithmetical skills, the use of mathematics isnot avoided, and all the mathematics required is taught asthe reader progresses.

Each book is a complete treatise of a particular branchof the subject and, therefore, can be used on its own with oneproviso, that the later books do not duplicate material fromtheir predecessors, thus a working knowledge of the subjectscovered by the earlier books is assumed.

BOOK 1, This book contains all the fundamental theorynecessary to lead to a full understanding of the simple elec-tronic circuit and its main components.

BOOK 2: This book continues with alternating current'theory without which there can be no comprehension of speech, music, radio, television or even the electricityutilities.

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PH241: DC ELECTRONICS $17.45Covers everything from voltage current, and resistance rela-tionships to more advanced studies of electricalmeasurements, circuits, resistors, capacitors, and inductors,

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PF1243: ELECTRONICS CIRCUITS $17.45Covers all of the most popular electronic circuits, with em-phasis on integrated circuits.

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Tab1531: CONCEPTS OF DIGITAL ELECTRONICS $22.45This book erases the mysteries surrounding digital elec-tronics theory. Understand and use low-cost 7400 series IC'sto produce working digital devices including a power supplyand a breadboard experimenter.

PROJECTSBPI& ELECTRONIC ROJECTS FOR BEGINNERS $5.90E.G. RAYER, T.Eng.(CEI), Assoc-IEREAnother book written by the very experienced author - Mr.F.G. Rayer - and in it the newcomer to electronics, will finda wide range of easily made projects. Also, there are a con-siderable number of actual component and wiring layouts, toaid the beginner.

Furthermore, a number of projects have been arrangedso that they can be constructed without any need for solder-ing and, thus, avoid the need for a soldering iron.

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221: 28 TESTED TRANSISTOR ROJECTSR.TORRENS $5.50Mr. Richard Torrens is a well experienced electronicsdevelopment engineer and has designed, developed, builtand tested the many useful and interesting circuits includedin this book. The projects themselves can be split down intosimpler building blocks, which are shown separated by boxesin the circuits for ease of description, and also to enable anyreader who wishes to combine boxes from different projectsto realise ideas of his own.

BP49: POPULAR ELECTRONIC PROJECTS $6.25RA. PENFOLDIncludes a collection of the most popular types of circuitsand projects which, we feel sure, will provide a number ofdesigns to interest most electronics constructors. The pro-jects selected cover a very wide range and are divided intofour basic types: Radio Projects, Audio Projects, HouseholdProjects and Test Equipment.

EXPERIMENTER'S GUIDE TO SOLID STATE ELECTRONICPROJECTSABOO7 $10.45An ideal sourcebook of Solid State circuits and techniqueswith many practical circuits. Also included are many usefultypes of experimenter gear.

B P71: ELECTRONIC HOUSEHOLD ROJECTS $7.70R. A. PENFOLDSome of the most useful and popular electronic constructionprojects are those that can be used in or around the home.The circuits range from such things as '2 Tone Door Buzzer',Intercom, through Smoke or Gas Detectors to Baby andFreezer Alarms.

1P94: ELECTRONIC PROJECTS FOR CARS AND BOATS 18.10R.A. PENFOLDProjects, fifteen in all, which use a 12V supply are the basisof this book. Included are projects on Windscreen WiperControl, Courtesy Light Delay, Battery Monitor, CassettePower Supply, Lights Timer, Vehicle Immobiliser, Gas andSmoke Alarm, Depth Warning and Shaver Inverter.

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PH250: EXPERIMENTER'S GUIDE TO SOLID STATEELECTRONICS PROJECTSA. BARBER $10.45This book takes the mystery out of solid state electronics andenables the reader to build such useful devices as: seriesregulated power supplies, light dimmers. solar cell operatedradios, hi-fi amplifiers, light indicators for battery operatedequipment and much more

110 THYRISTOR PROJECTS USING SCRs AND TRIACSMARSTONH822 $13.45A grab bag of challenging and useful semiconductor projectsfor the hobbyist, experimenter, and student. The projectsrange from simple burglar, fire, and water level alarms tosophisticated power control devices for electric tools andtrains. Integrated circuits are incorporated wherever their usereduces project costs.

110 CMOS DIGITAL IC PROJECTSMARSTONHB23 $11.75Outlines the operating characteristics of CMOS digital ICsand then presents and discusses 110 CMOS digital IC circuitsranging from inverter gate and logic circuits to electronicalarm circuits. Ideal for amateurs, students and professionalengineers.

B P76: POWER SUPPLY PROJECTS $7.30LA. PENFOLDLine power supplies are an essential part of many electronicsprojects. The purpose of this book is to give a number ofpower supply designs, including simple unstabilised types,fixed voltage regulated types, and variable voltage stabiliseddesigns, the latter being primarily intended for use as benchsupplies for the electronics workshop. The designs providedare all low voltage types for semiconductor circuits.

There are other types of power supply and a number ofthese are dealt with in the final chapter, including a cassettepower supply, Ni-Cad battery charger, voltage step up circuitand a simple inverter.

BP84: DIGITAL IC PROJECTS $8.10E.G. RAYER, T.Eng.(CEI),Assoc.IEREThis book contains both simple and more advanced projectsand it is hoped that these will be found of help to the readerdeveloping a knowledge of the workings of digital circuits.To help the newcomer to the hobby the author has includeda number of board layouts and wiring diagrams. Also themore ambitious projects can be built and tested section bysection and this should help avoid or correct faults thatcould otherwise be troublesome. An ideal book for bothbeginner and more advanced enthusiast alike.

B P67: COUNTER DRIVER AND NUMERAL DISPLAYPROJECTS $7.55F.G. RAYER, T.Eng.(CEI), Assoc. IERENumeral indicating devices have come very much to theforefront in recent years and will, undoubtedly, find increas-ing applications in all sorts of equipment. With present dayintegrated circuits, it is easy to count, divide and displaynumerically the electrical pulses obtained from a great rangeof driver circuits.

In this book many applications and projects usingvarious types of numeral displays, popular counter anddriver IC's etc. are considered.

B P73: REMOTE CONTROL PROJECTS $8.60OWEN BISHOPThis book is aimed primarily at the electronics enthusiastwho wishes to experiment with remote control. Full explana-tions have been given so that the reader can fully understandhow the circuits work and can more easily see how to modifythem for other purposes, depending on personal re-quirements. Not only are radio control systems consideredbut also infra -red, visible light and ultrasonic systems as arethe use of Logic ICs and Pulse position modulation etc.

B M MINI -MATRIX BOARD PROJECTS $8.10LA. PENFOLDTwenty useful projects which can all be built on a 24 x 10hole matrix board with copper strips. Includes Doorbuzzer,Low -voltage Alarm, AM Radio, Signal Generator, ProjectorTimer, Guitar Headphone Amp, Transistor Checker andmore.

BP103: MULTI -CIRCUIT BOARD PROJECTS $8.10R.A. ENFOLDThis book allows the reader to build 21 fairly simple elec-tronic projects, all of which may be constructed on the sameprinted circuit board. Wherever possible, the same com-ponents have been used in each design so that with arelatively small number of components and hence low cost,it is possible to make any one of the projects or by re -usingthe components and P.C.B. all of the projects.

Tab1431: DIGITAL ELECTRONIC PROJECTS $21.45Build a deluxe code oscillator, a digital game called Climb -the -Mountain, a clock with alarm, a metric measuring wheel,a modular decade counter, even a 14 -note music generator17 projects in all.

B P107: 30 SOLDERLESS BREADBOARD PROJECTS -B OOK 1 $9.35R.A. PENFOLDA "Solderless Breadboard" is simply a special .board onwhich electronic circuits can be built and tested. The com-ponents used are just plugged in and unplugged as desired.The 30 projects featured in this book have been speciallydesigned to be built on a "Verobloc" breadboard. Whereverpossible the components' used are common to several pro-jects, hence with only a modest number of reasonably inex-pensive components it is possible to build, in turn, every Pro-ject shown.

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BP106: MODERN OP -AMP PROJECTS $5.10RA. PENFOLDFeatures a wide range of constructional projects which makeuse of op -amps including low -noise, low distortion, ultra -highinput impedance, high slew -rate and high output currenttypes

CIRCUITS

B P80: POPULAR ELECTRONIC CIRCUITS -B OOK 1 $8.25R.A. PENFOLDAnother book by the very popular author, Mr. R.A. Penfold,who has designed and developed a large number of variouscircuits. These are grouped under the following generalheadings; Audio Circuits, Radio Circuits, Test Gear Circuits,Music Project Circuits, Household Project Circuits andMiscellaneous Circuits.

B P98: POPULAR ELECTRONIC CIRCUITS, BOOK 2 $9.35R.A. PENFOLD70 plus circuits based on modern components aimed at thosewith some experience.

The GIANT HANDBOOK OF ELECTRONIC CIRCUITSTAB No.1300 $28.45About as twice as thick as the Webster's dictionary, and hav-ing many more circuit diagrams, this book is ideal for any ex-perimenter who wants to keep amused for several centuries.If there isn't a circuit for it in here, you should have no dif-ficulty convincing yourself you don't really want to build it.

B P39: 50 (FET) FIELD EFFECT TRANSISTORPROJECTS $5.50E.G. BAYER, T.Eng.(CEI),Assoc.IEREField effect transistors (FETs), find application in a widevariety of circuits. The projects described here include radiofrequency amplifiers and converters, test equipment andreceiver aids, tuners, receivers, mixers and tone controls, aswell as various miscellaneous devices which are useful in thehome.

This book contains something of particular interest forevery class of enthusiast - short wave listener, radioamateur, experimenter or audio devotee.

BPB7: SIMPLE L.E.D. CIRCUITS $5.90RN. SOARSince it first appeared in 1977, Mr. R.N. Soar's book has prov-ed very popular. The author has developed a further range ofcircuits and these are included in Book 2. Projects include aTransistor Tester, Various Voltage Regulators, Testers and soon.

BP42: 50 SIMPLE L.E.D. CIRCUITS $3.55R.N. SOARThe author of this book, Mr. R.N. Soar, has compiled 50 in-teresting and useful circuits and applications, covering manydifferent branches of electronics, using one of the most inex-pensive and freely available components - the Light Emit-ting Diode (L.E.D .L A useful book for the library of bothbeginner and more advanced enthusiast alike.

BP82: ELECTRONIC PROJECTS USINGSOLAR CELLS $8.10OWEN BISHOPThe book contains simple circuits, almost all of whichoperate at low voltage and low currents, making themsuitable for being powered by a small array of silicon cells.The projects cover a wide range from a bicyle speedometerto a novelty 'Duck Shoot'; a number of power supply circuitsare included.

BP37: 50 PROJECTS USING RELAYS,SCR's & TRIACS $5.50F.G.RAYER, T.Eng.(CEI),Assoc.IERERelays, silicon controlled rectifiers (SCR's) and bi-directionaltriodes (TRIACs) have a wide range of applications in elec-tronics today. This book gives tried and practical working cir-cuits which should present the minimum of difficulty for theenthusiast to construct. In most of the circuits there is a widelatitude in component values and types, allowing easymodification of circuits or ready adaptation of them to in-dividual needs.

BP24: 50 PROJECTS USING IC741 $4.25RUDI a UWE REDMERThis book, originally published in Germany by TOPP, hasachieved phenomenal sales on the Continent and Babanidecided, in view of the fact that the integrated circuit used inthis book is inexpensive to buy, to make this unique bookavailable to the English speaking reader. Translated from theoriginal German with copious notes, data and circuitry, a"must" for everyone whatever their interest in electronics.

VMOS PROJECTS $8.20RA. PENFOLDAlthough modern bipolar power transistors give excellentresults in a wide range of applications, they are not withouttheir drawbacks or limitations. This book will primarily beconcerned with VMOS power FETs although powerMOSFETs will be dealt with in the chapter on audio circuits.A number of varied and interesting projects are covered

Generatorthe main headings of: Audio Circuits, Sound

Generator Circuits, DC Control Circuits and Signal ControlCircuits.

BP44: IC 555 PROJECTS $7.55E.A. PARR, B.Sc.,C.Eng., M.I.E.E.Every so often a device appears that is so useful that onewonders how life went on before without it. The 555 timer issuch a device. Included in this book are Basic and GeneralCircuits, Motor Car and Model Railway Circuits, Alarms andNoise Makers as well as a section on the 556, 558 and 559timers.

B P6S: SINGLE IC PROJECTS $6.55RA.PENFOLDThere is now a vast range of ICs available to the amateurmarket, the majority of which are not necessarily designedfor use in a single application and can offer unlimitedpossibilities. All the projects contained in this book are sim-ple to construct and are based on a single IC. A few projectsemploy one or two transistors in addition to an IC but in mostcases the IC is the only active device used.

BP97: IC PROJECTS FOR BEGINNERS $8.10F.G. RAVERCovers power supplies, radio, audio, oscillators, timers andswitches. Aimed at the less experienced reader, the com-ponents used are popular and inexpensive.

BP841: HOW TO USE OP AMPS $9.35E.A. PARRA designer's guide covering several op amps, serving as asource book of circuits and a reference book for designcalculations. The approach has been made as non -mathematical as possible.

X ARRAY COOKBOOKJUNGH826 $14.25

aimed at solving electronic circuit ap-plication problems by using IC arrays. An IC array, unlikespecific -purpose ICs, is made up of uncommitted IC activedevices, such as transistors, resistors, etc. This book coversthe basic types of such ICs and illustrates with examples howto design with them. Circuit examples are included, as well asgeneral design information useful in applying arrays.

BP50: IC LM3900 PROJECTS $5.90H.KYBETT,B.Sc., C.Eng.The purpose of this book is to introduce the LM3900 to theTechnician, Experimenter and the Hobbyist. It provides thegroundwork for both simple and more advanced uses, and ismore than just a collection of simple circuits or projects.

Simple basic working circuits are used to introduce thisIC. The LM3900 can do much more than is shown here, this isjust an introduction. Imagination is the only limitation withthis useful and versatile device. But first the reader mustknow the basics and that is what this book is all about.

223: 50 PROJECTS USING IC CA3130 $5.50LA.PENFOLDIn this book, the author has designed and developed anumber of interesting and useful projects which are dividedinto five general categories: I - Audio Projects II - R.F.Projects III - Test Equipment IV - Household Projects V- Miscellaneous Projects.

224: SO CMOS IC PROJECTS $4.25R.A. PENFOLDCMOS IC's are probably the most versatile range of digitaldevices for use by the amateur enthusiast. They are suitablefor an extraordinary wide range of applications and are alsosome of the most inexpensive and easily available types ofIC.

Mr. R.A. Penfold has designed and developed a numberof interesting and useful projects which are divided into fourgeneral categories: I - Multivibrators II - Amplifiers andOscillators III - Trigger Devices IV - Special Devices.

THE ACTIVE FILTER HANDBOOKTAB No.1133 $14.45Whatever your field - computing, communications, audio,electronic music or whatever - you will find this book theideal reference for active filter design.

The book introduces filters and their uses. The basicmath is discussed so that the reader can tell where all designequations come from. The book also presents many practicalcircuits including a graphic equalizer, computer tape inter-face and more.

DIGITAL ICS - HOW THEY WORK AND HOW TO USETHEMABOO4 $11.45An excellent primer on the fundamentals of digital elec-tronics. This book discusses the nature of gates and relatedconcepts and also deals with the problems inherent to prac-tical digital circuits.

MASTER HANDBOOK OF 1001 PRACTICAL CIRCUITSTAB No.B00 $20.45MASTER HANDBOOK OF 1001 MORE PRACTICAL CIR-CUITSTAB No.804 $24.45Here are transistor and IC circuits for just about any applica-tion you might have. An ideal source book for the engineer,technician or hobbyist. Circuits are classified according tofunction, and all sections appear in alphabetical order.

THE MASTER IC COOKBOOKTAB No.1199 $18.45If you've ever tried to find specs for a so called 'standard'chip, then you'll appreciate this book. C.C. Hallmark hascompiled specs and pinout for most types of ICs that you'dever want to use.

ELECTRONIC DESIGN WITH OFF THE SHELF INTEGRATEDCIRCUITSAB016 $13.45This practical handbook enables you to take advantage ofthe vast range of applications made possible by integrated'circuits. The book tells how, in step by step fashion, to selectcomponents and how to combine them into functional elec-tronic systems. If you want to stop being a "cookbook hob-byist", then this is the book for you.

BP117: PRACTICAL ELECTRONIC BUILDING BLOCKSBOOK 1 $8.10Virtually any electronic circuit will be found to consist of anumber of distinct stages when analysed. Some circuits in-evitably have unusual stages using specialised circuitry, butin most cases circuits are built up from building blocks ofstandard types.

This book is designed to aid electronics enthusiasts wholike to experiment with circuits and produce their own pro-jects rather than simply follow published project designs.

The circuits for a number of useful building blocks areincluded in this book. Where relevant, details of how tochange the parameters of each circuit are given so that theycan easily be modified to suit individual requirements.

P14253: ELECTRONIC DESIGNWITH OFF -THE -SHELF INTEGRATED CIRCUITSZ. MEIKEIN & P. TACKRAY $13.45A real help for do-it-yourselfers, this handy guide tells profes-sionals and hobbyists alike, how to take components off theshelves, arrange them into circuitry, and make any systemperform its desired function.

AUDIOBP90: AUDIO PROJECTS $8.10F.G. BAYERCovers in detail the construction of a wide range of audioprojects. The text has been divided into preamplifiers andmixers, power amplifiers, tone controls and matching andmiscellaneous projects.

205: FIRST BOOK OF HI-FI LOUDSPEAKERENCLOSURES $3.55

BABANIThis book gives data for building most types of loudspeakerenclosure. Includes corner reflex, bass reflex, exponentialhorn, folded horn, tuned port, klipschorn labyrinth, tunedcolumn, loaded port and multi speaker panoramic. Manyclear diagrams for every construction showing the dimen-sions necessary.

BP47: MOBILE DISCOTHEQUE HANDBOOK $5.90COLIN CARSONThe vast majority of people who start up "Mobile Discos"know very little about their equipment or even what to buy.Many people have wasted a "small fortune" on poor, un-necessary or badly matched apparatus.

The aim of this book is to give you enough informationto enable you to have a better understanding of manyaspects of "disco" gear.

140W TO BUILD A SMALL BUDGET RECORDING STUDIOFROM SCRATCH. . .

TAB No.1166 $16.45The author, F. Alton Everest, has gotten studios togetherseveral times, and presents twelve complete, tested designsf 6r a wide variety of applications. If all you own is a monocassette recorder, you don't need this book. If you don't wantyour new four track to wind up sounding like one, though,you shouldn't be without it.

BP51: ELECTRONIC MUSIC AND CREATIVE TAPERECORDING $5.50M.K. BERRYElectronic music is the new music of the Twentieth Century.It plays a large part in "pop" and "rock" music and, in fact,there is scarcely a group without some sort of synthesiser orother effects generator.

This book sets out to show how electronic music can bemade at home with the simplest and most inexpensive ofequipment. It then describes how the sounds are generatedand how these may be recorded to build up the final com-position

BP74: ELECTRONIC MUSIC PROJECTS $7.70RA. PENFOLDAlthough one of the more recent branches of amateur elec-tronics, electronic music has now become extremely popularand there are many projects which fall into this category. Thepurpose of this book is to provide the constructor with anumber of practical circuits for the less complex items ofelectronic music equipment, including such things as a FuzzBox, Waa-Waa Pedal, Sustain Unit, Reverberation andPhaser-Units, Tremelo Generator etc

58-DECEMBER-1983-ETI See order form in this issue. All prices Include shipping. No sales tax applies.

Electronics8P81: ELECTRONIC SYNTHESISER PROJECTS $7.30M.K. BERRYOne of the most fascinating and rewarding applications ofelectronics is in electronic music and there is hardly a grouptoday without some sort of synthesiser or effects generator.Although an electronic synthesiser is quite a complex pieceof electronic equipment, it can be broken down into muchsimpler units which may be built individually and these canthen be used or assembled together to make a complete in-strument.

ELECTRONIC MUSIC SYNTHESIZERSTAB No.1167 $11.45If you're fascinated by the potential of electronics in thefield of music, then this is the book for you. Included is dataon synthesizers in general as well as particular models. Thereis also a chapter on the various accessories that areavailable.

Tab1364: DESIGNING, BUILDING AND TESTINGYOUR OWN SPEAKER SYSTEM... WITH PROJECTS $14.45Covers the theory of speaker construction and describes avariety of plans for speaker system projects ranging fromsimple setups to complex multi -driver systems. Enclosuredesign is covered in very good detail.

BP68: CHOOSING AND USING YOUR HI-FI $7.25MAURICE L. JAYThe main aim of this book' is to provide the reader with thefundamental information necessary to enable him to make asatisfactory choice from the extensive range of hi-fi equip-ment now on the market.

Help is given to the reader in understanding the equip-ment he is interested in buying and the author also gives hisown opinion of the minimum standards and specificationsone should look for. The book also offers helpful advice onhow to use your hi-fi properly so as to realise its potential. AGlossary of terms is also included.

TEST EQUIPMENT

BP75: ELECTRONIC TEST EQUIPMENTCONSTRUCTION $7.30F.G. RATER, T.Eng. (CEI), Assoc. !EREThis book covers in detail the construction of a wide range oftest equipment for both the Electronics Hobbyists and RadioAmateur. Included are projects ranging from an FETAmplified Voltmeter and Resistance Bridge to a FieldStrength Indicator and Heterodyne Frequency Meter. Not on-ly can the home constructor enjoy building the equipmentbut the finished projects can also be usefully utilised in thefurtherance of his hobby.

99 TEST EQUIPMENT PROJECTS YOU CAN BUILDTAB No.805 $16.45An excellent source book for the hobbyist who wants to buildup his work bench inexpensively. Projects range from a sim-ple signal tracer to a 50MHz frequency counter. There arecircuits to measure just about any electrical quantity:voltage, current, capacitance, impedance and more. Thevariety is endless and includes just about anything you couldwish fort

HOW TO GET THE MOST OUT OF LOW COST TEST EQUIP-MENTAB017 $10.45Whether you want to get your vintage 1960 'TestRite'signalgenerator working, or you've got something to measure withnothing to measure it with, this is the book for you. Theauthor discusses how to maximize the usefulness of cheaptest gear, how to upgrade old equipment, and effective testset ups.

THE POWER SUPPLY HANDBOOKTAB No.806 $16.45A complete one stop reference for hobbyists and engineers.Contains high and low voltage power supplies of every con-ceivable type as well mobile and portable units.

PH246: ELECTRONIC TEST EQUIPMENT $20.45Covers analog and digital meters, oscilloscopes, frequencygeneration and measurement, and special measuring in-struments.

Tab1532: THE COMPLETE BOOK OFOSCILLOSCOPES $20.45This totally up-to-date handbook is both an in-depthreference source and a practical applications guide. Informa-tion is included on both ordinary service and laboratory'scopes, waveform analysis, vectors, vectorscopes, high andlow frequency analysis, sampling, storage, digital scopes,and signature analysis. The author, Stan Prentiss is one of theleading technical writers in the U.S.

INTERRELATED INTEGRATED ELECTRONICS CIRCUITSFOR THE RADIO AMATEUR, TECHNICIAN, HOBBYIST ANDCB'ERMENDELSONH829 $11.45This book provides a variety of appealing projects that canbe constructed by anyone from the hobbyist to the engineer.Construction details, layouts, and photographs are providedto simplify duplication While most of the circuits are shownon printed circuit boards, every one can be duplicated onhand -wired, perforated boards. Each project is related toanother projects so that several may be combined into asingle package. The projects, divided into five major groups,include CMOS audio modules. passive devices tohelp in ben-chwork, test instruments, and games.

BASIC CARRIER TELEPHONY, THIRD EDITIONTALLEYH828 $16.45A basic course in the principles and applications of carriertelephony and its place in the overall communications pic-ture. It is abundantly illustrated, with questions and pro-blems throughout, and requires a minimum of mathematics.

Tab1309: THE ACOUSTIC AND ELECTRIC GUITARREPAIR HANDBOOK $25.00Literally everything the amateur or professional musicianneeds to know to properly maintain his instruments, plus allthe how-to's for making repairs from simple tuning to majoroverhau Is.

BP110: HOW TO GET YOUR ELECTRONIC PROJECTSWORKING $8.10R.A. PENFOLDWe have all built circuits from magazines and books only tofind that they did not work correctly, or at all, when first swit-ched on. The aim of this book is to help the reader overcomejust these problems by indicating how and where to startlooking for many of the common faults that can occur whenbuilding up projects.

ELECTRONIC TROUBLESHOOTING HANDBOOKA8019 $12.45This workbench guide can show you how to pinpoint circuittroubles in minutes, how to test anything electronic, and howto get the most out of low cost test equipment. You can useany and all of the time -saving shortcuts to rapidly locate andrepair all types of electronic equipment malfunctions.

COMPLETE GUIDE TO READING SCHEMATIC DIAGRAMSABO18 $10.45A complete guide on how to read and understand schematicdiagrams. The book teaches how to recognize basic circuitsand identify component functions. Useful for techniciansand hobbyists who want to avoid a lot of headscratching.

REFERENCE

BP135: INTERNATIONAL TRANSISTOR EQUIVALENTSGUIDE $12.25ADRIAN MICHAELSThis book will help the reader to find possible substitutes fora popular user -orientated selection of modern transistors.Also shown are the material type, polarity, manufacturerselection of modern transistors. Also shown are the materialtype, polarity, manufacturer and use. The Equivalents aresub -divided into European, American and Japanese. The pro-ducts of over 100 manufacturers are included. An essentialaddition to the library of all those interested in electronics,be they technicians, designers, engineers or hobbyists. Fan-tastic value for the amount of information it contains.

BP108: INTERNATIONAL DIODE EQUIVALENTS GUIDEADRIAN MICHAELS $8.35This book is designed to help the user in finding possiblesubstitutes for a large user orientated selection of the manydifferent types of semiconductor diodes that are availabletoday. Besides simple rectifier diodes also included areZener diodes, LEDs, Diacs Triacs, Thyristors, Photo diodesand Display diodes.

B PI: FIRST BOOK OF TRANSISTOR EQUIVALENTS ANDSUBSTITUTES $2.80B.B. BABANIThis guide covers many thousands of transistors showingpossible alternatives and equivalents. Covers transistorsmade in Great Britain, USA, Japan, Germany, France, Europe,Hong Kong, and includes types produced by more than 120different manufacturers.

B P14: SECOND BOOK OF TRANSISTOR EQUIVALENTSAND SUBSTITUTES $4.80B .B. BABANIThe "First Book of Transistor Equivalents" has had to bereprinted 15 times. The "Second Book" produced in the samestyle as the first book, in no way duplicates any of the datapresented in it. The "Second Book" contains only additionalmaterial and the two books complement each other andmake available some of the most complete and extensive in-formation in this field. The interchangeability data coverssemiconductors manufactured in Great Britain, USA, Ger-many, France, Poland, Italy, East Germany, Belgium. Austria,Netherlands and many other countries.

TOWER'S INTERNATIONAL OP -AMP LINEAR IC SELECTORTAB No.1216 $13.45This book contains a wealth of useful data on over 5,000 Op -amps and linear ICs - both pinouts and essentialcharacteristics. A comprehensive series of appendices con-tain information on specs, manufacturers, case outlines andso on.

CMOS DATABOOKTAB No.984 $9.95There are several books around with this title, but most areKist collections of manufacturers' data sheets. This one, byBill Hunter, explains all the intricacies of this useful family oflogic devices . the missing link in getting your owndesigns working properly. Highly recommended to anyoneworking with digital circuits.

Tab1538: ELECTRONIC DATABOOK - 3RD EDITION $30.00Any electronic job will be easier and less time consumingwhen you have instant access to exactly the nomogram,table, chart or formula you need, when you need it. All thisand much more is included in this completely revised and up-dated version of one of the most respected informationsource in the electronics field. Generously indexed, thishandbook is divided into six sections: Frequency Data; Com-munication; Passive Components; Active Components;Mathematical Data; Formulas and Symbols and PhysicalData.

Tab1516: TOWERS INTERNATIONALMICROPROCESSOR SELECTOR $31.45Towers Selector books have gained an international reputa-tion for completeness and usefulness. This volume gives youall the data you will normally need to select the right chip.

ROBOTICSTHE COMPLETE HANDBOOK OF ROBOTICSTAB No.1071 $16.45All the information you need to build a walking, talkingmechanical friend appears in this book. Your robot can takemany forms and various options - light, sound, and proximi-ty sensors - are covered in depth.

HOW TO BUILD YOUR OWN SELF PROGRAMMINGROBOTTAB No.1241 $14.45A practical guide on how to build a robot capable of learninghow to adapt to a changing enviroment. The creaturedeveloped in the book, Rodney, is fully self programming,can develop theories to deal with situations and apply thosetheories in future circumstances.

Tab1421: HANDBOOK OF ADVANCED ROBOTICS $24.45Here's the key to learning how today's sophisticated robotmachines operate, how they are controlled, what they can doand how you can put this modern technology to work. Alsoincluded are details on building your own hobby robot.

BUILD YOUR OWN WORKING ROBOTTAB No.841 $11.45Contains complete plans - mechanical, schematics, logicdiagrams and wiring diagrams - for building Buster. Busteris a sophisticated experiment in cybernetics you can build instages. There are two phases involved: first Buster is leashled, dependent on his creator for guidance; the second phasemakes Buster more independent and able to get out of toughsituations.

VIDEOBP100: AN INTRODUCTION TO VIDEOD.K. MATHEWSON $8.10Presents in as non -technical a way as possible how a videorecorder works and how to get the best out of it and its ac-cessories. Among the items discussed are the pros and consof the various systems, copying and editing, internationaltape exchange and understanding specifications.

Tab1519: ALL ABOUT HOME SATELLITETELEVISION $23.45Covers such aspects as where to buy, problems in setting upyour TVRO station and how to solve them, antenna sitingand equipment selection.

Tab1490: VIDEO CASSETTE RECORDERS:BUYING, USING AND MAINTAINING $14.45A complete handbook for the video enthusiast. You'll learnabout how the systems work and how to choose as well astake a technical look at the inside workings. There are alsosections on making your own video recordings.

MISCELLANEOUSBP101: HOW TO IDENTIFY UNMARKED IC'S $2.70KH. RECORROriginally published as a feature in 'Radio Electronics', thischart shows how to record the particular signature of an un-marked IC using a test meter, this information can then be us-ed with manufacturer's data to establish the application.

AUDIO AND VIDEO INTERFERENCE CURESKAHANERHB21 $9.45A practical work about interference causes and cures that af-fect TV, radio, hi -f i, CB, and other devices. Provides all the in-formation needed to stop interference. Schematic wiringdiagrams of filters for all types of receivers and transmittersare included. Also, it supplies simple filter diagrams toeliminate radio and TV interference caused by noisy homeappliances, neon lights, motors, etc.

BASIC TELEPHONE SWITCHING SYSTEMSTALLEYH827 $16.00The Revised Second Edition of this book, for trainee andengineer alike, includes updated statistical data ontelephone stations, and new and improved signaling methodsand switching techniques. It also includes E & M signaling in-terface for electronic central off ices and automatic numberidentification methods used in step-by-step, panel andcrossbar central offices.

ET[ -DECEMBER -1983-59See order form in this issue. All prices include shipping. No sales tax applies.

Playmate Part IIFor aspiring artists weconclude our portableguitar amp with added in-gredients fuzz and wah.Design and developmentby Phil Walker.

BEFORE WE CONTINUE with ouranalysis of the circuit theory, we have toapologize for the manpower shortage lastmonth which meant that the Playmate cir-cuit diagram missed out on our usualthorough checking. Naturally the perver-sity of the universe ensured that this wasthe project that had several errors, sowe're reprinting the circuit diagram withmistakes and duplicate componentnumbers corrected and all pots markedCW or CCW to tie up with the front panelwiring diagram. Meanwhile, back to theplot . . .

The State -variable FilterThings start getting a bit heavy now! Thefollowing equations are the transfer equa-tions for a state -variable filter such as thatin Fig. 2:

V [(R1/R3) x V,,, + (R2/R3) x+ R5/(R4 + R5)x [1 + R3(R1 + R3)/(R1R2)] x VoIf R1 = R2 = R3 = R5, then:V), = - (V, + Vy) + R1(1 + 2)/(R4 + R1) x Vo

3R1V0V), (V, + Vy)

R4 + R1Vo -1/sCR x V ,

V = - sCR VoV, = -1/sCR x Vo

Substitute (2) and (3) in (1):

- sCR Vo3R1 Vo

(R1 + R4)- (V,,, + (-1)/sCR V.)

vin-_ (sCR + 3R1/(R1 + R4) + i/sCR)

+ 1/jo.CR

frequency

vo

= jo.CR +(R1 + R4)

(s = jco, w - 27r f, f =

3R1

Fig. 1. (Right) The correct version of the circuitdiagram - sorry ...

Compare this with the equation for anLCR tuned circuit:

V, = (jwL + 1/(j(.0C) + R) loot(Fig. 3)

V,- jwL + R + i/(jwC) (LCR circuit)lout

V, 3R1jcoCR + + 1 /(jokR)

Vow (R1 + R4)(State variable filter)

From this it is apparent that theseresponses are similar except that the LCRcircuit gives a current output rather than avoltage. For this type of LCR circuit, thefrequency of minimum attenuation ormaximum gain (the resonant frequency) isgiven by:

1

f =27rVIC

NOTE:IC1 IS'CA3140IC2,4 RE LM13600IC3 IS TL084ICS IS TL082IC6 IS 74101,2,5 ARE 2N390503,4 ARE 2N390406 IS TIP32A07 IS TIP31AD1-5 ARE 1N4148

01

C23680n

+VE

R3922k

2

X 1.--e-PIA/S^.1

100kR36 41

v.

R3710k

6

0-VE

R3810k

5,7

R40100k

R67100k


For our circuit this is: - As we are using a capacitative load, thisoutput current will generate a voltage of.

1 1

22-N/CR.CR 2TCR

The 'Q' factor influencing the bandwidthis given by:

Vou, = 1., xjwC

1

= V x x26 x 10-3 jcoC

R1 labc 1

27r f L 27r x (1/27rCR) x CR =V,Q - R1 + R 26 x 10' jwC

R 3R1/(R1 + R4)R1 + R4

3R1

Figure 4 shows the configurationnecessary to use the LM13600 as a filter ofthis type. Last month we found that thetransfer function of the LM13600 with nodiode current is given by:

lout -labc

26 x 10-3X Vin

labc

Fig. 2. Generalized state -variable filter.

Since we are not dealing with a nor-mal type of op -amp, analysis of the circuitis not as easy as the normal filter, but theresult is an equation of much the sameform. We do not show all the derivationhere as it would occupy most of a page.However, the end result is that the centrefrequency of the filter pass band is pro-portional to the amplifier bias current.Therefore we have an easy way to controlthe wah wah effect.

R1210k

VE

4R14 R1515k 15k

V1/V R16220k

oiD3

10,12

11 C4 D4, R10

47R -VE 470n

9 13

+

CW 171005

12

C3 R1322u 1k0

CCW

Q2

I9

--VE

C9470n

R68105

FUZZ

OFF S1N1a

R78 2

470k 1 2

C5680n

R1910M10M

ICIC

A/1112112M2

SW16OFF

-1-VE

WAHOFF

C6470n

CW RV2a Dm R2150k 10k

EFFECTWIDTH

_11-C27 It C2910u T 10u

OV

+ C26 + C2811TT10" . VE

RV5100kVOL

ICSa

4

AUTO

PEDAL

OFF

TREBLE846

CCW R2T CWR48 .vE

22k CW10k1-1.1A,V1- R64

C13 C14 47

10n

VE C12 C15680n 33n

R22

SW2a

4

L

834470k

VE

R45R44 100k100k

R4710k

10n

R494M7

6R50105

BASS

CCW CW

RV7100k

C1615n

TONE CONTROL

56

R5110k

R3315k

-VE

VE

R2622k

R24R23 22k C7 R28 R29 -VE C8

1n5 150 150 1n5150

WAHFREOCW

RV3100k

CCW

835D5 1k0

R62 47R

R275k6

-VE

C17

F3531.C18100k P C19

10u

R5610k

R58150

POWER AMP

PEDAL

AUTO

SW2b

9

R30556

-VE

OUTPUTTO

SPEAKER

1OI- C20100n

C241000u

R31100k

+9V FROMBATTERY

OV

- 9V FROMBATTERY

:.251000u

ETI-DECEMBER--1983-61

Playmate Pt. 2

ig. 3. Generalized LCR tuned circuit.

Fig. 5. (Right) Component overlay for the pre-amplifier board.

Fig. 6. (Below) Overlay for the tone controlboard.

Fig. 7. (Far Right) Overlay for the powerof the Playmate.

SW2.AUTO,

SW,.10F F)

COM

i

[1111CID 01-0-;;; "

CPUTCOM

"'X;

SW]NORMAL

SW21,POLE

SW2b RVIIPEDAL. WIPERAUTO)

RV3 WIPER

RV1 CW

SW1.10 F.2)

ROI COM

RV3CW

RV3 5W2.CCW ,POLE OFF(

SINIs(POLE)SWIII 11.2)

RV2bCCW

RV2b WIPERARO CW

RI/2 WIPERAND CCW

VE INCONTROL

IAIILTONE

TgENTROVE NCOIOL

Rye COW

RV7 CCW

RV5 COM

RV5 CPI

CW CLOCKWISE WHEN SEENFROM THE FRONT

CCW- COUNTERCLOCKWISE

C21

TO PREAP.r

VE IN FROMPOWER NAP

RV6 CW\7( RAE 444

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OUT TO POWER AMP

RV7 CM

OV IN FROM POWER AMP

RV7 WIPER

RV6 WIPER

OV OUT TO PREAMP

VE IN FROMPOWER AMP

VE OUT TO PREAPAP

.;Suggeste,4 A.0 Adapter

120VAC

Parts ListR1,2 270R 1/4W 5%C1,2 4700u 25 V electrolyticICI 7805IC2 7905ZDI,2 3V9 400 mW zenerBR1 1 amp bridge rectifier

T1

SW1

FS1LP 1

06

Ill

fIV FROMBATTERYIA SWITCH -

VE TOTONE

CONTROL

a

qa

NE ATSINK

OUT TO SPEAKER

t

OV TO TONECONTROL

+ C26

07

III

VE TO TONE

-9V FROM BATTERYVIA SWITCH (ROE)

.05nn CONTROL

- OV FROM BATTERIESVIA $WITCH (RVO)

WIIIIEN CONNECTIONFOR INPUT(CONNECT TellENO ONLY)

INPUT FROM TONECONTROL

V

9-0-9 12 VA transformer, 100mA or moreDPDT miniature rocker or slideswitch1 A 200 mm fuse and holder120 V panel neon with integralresistor

ConstructionExcept for the controls, almost all thecomponents for this project are mountedon the three PCBs. The preamplifierboard is the largest and most denselypacked. It is advisable to use sockets forthe ICs and don't forget the links. Thecapacitors used in the project should be assmall as possible, otherwise you will havedifficulty fitting them. A fine tippedsoldering iron will be useful whenassembling the boards and care should betaken to avoid creating short circuits bet-ween tracks with accidental soldersplashes.

Ensure that all the diodes, transistorsand other polarized components (especial-ly IC3) are fitted the correct way round.On the power amplifier board the outputtransistors are mounted on top of a shortlength of 1/2" x 1/2" aluminum anglewhich acts as a heatsink. The transistorsand the angle are held in position by thetransistor mounting screws.


PARTS LIST

Resistors (All 1/4W 5%)R1,3,42,43 47kR2,5,6,12,21,25,32,37,38,46-48,50-52,55,56,68 10kR8 220kR7,18,34 470k48 6k8R9,14,15,33 15kR10,62-65 47RR11,17,31,36,40,44,45,53,67 100kR13,22,23,28,29,35,57,58R19R20R24,26,39R27,30,41R49R54R59,60R61R66

1k010M2M222k5k64M733k2R26R8IMO

Potentiometers IC2,4 LM13600RV1,3,7 100k linear IC3 TL084RV2 50k linear dual gang IC5 TL082RV4 100k linear dual gang IC6 741RV5 100k logarithmic with two -pole Q1,2,5 2N3905 or equiv.

switch Q3,4 2N3904 or equiv.RV6 22k linear Q6 TIP32 or equiv.RV8 47k miniature horizontal preset Q7 TIP31 or equiv.

D1-5 1N4148Capacitors (All polycarbonate except wherestated)C1,5,10-1217,23 680nC2 220nC3 22u 16 V tantalumC4,6,9 470nC7,8 1n5C13,14 10nC15 33nC16 15nC18 68pC19 10u 35 V tantalumC20 100nC21,22,24,25C26-29 47u 10 V PCB electrolytic

1000u 10 V axial electrolytic

SemiconductorsICI CA3140

MiscellaneousSW1,2 2 -pole, 3 -way miniature slide

switchSW3 1 -pole, 2 -way miniature slide

switch

PCBs; case (220 x 105 x 230mm), Vero Ref.75-2443A; wire (single, single screened anddouble screened); 4" or 5" loudspeaker (8ohms, 5 W); standard 1/4" jack socket forinput; stereo jack socket for foot switch (ifrequired); 75 mm or 12 x 12 mm aluminumangle; two 9V batteries and clips.

1k0

100k

Fig. 4. Using the LM13600 as a state -variable filter.

Suggested Foot Pedal

CONTROL

CONTROL TO SW2

VE SUPPLY

VE SUPPLY

The first diagram shows the circuit usedwith a three -connection (stereo) jack. Thiswill duplicate the effect of the panel -mounted control. As the angular rotationof foot pedal controls is sometimes limited,

-VE SUPPLY

some adjustment of position may benecessary to get best results. If the range ofcontrol isn't wide enough, change to ahigher value. The link on SW2a should beremoved for this circuit. The seconddiagram shows a simple circuit for use withordinary jack connectors which can be usedif the link between SW2a pole and off posi-tion is retained.

Fig. 8. How to wire the front panel. Compare with the front panel photo last month.

Mount the control switches andpotentiometers on the front panel (seephoto for our layout) and make thenecessary interconnections and fit thethree components needed around thebalance control. The wiring from thefront panel preamplifier/effectsand the tone control boards should be car-ried out using thin flexible wire for controlsignals and miniature screened cable forany sound signals. These should be short,but allow enough slack to be able to fitthem in position easily (it is probablyeasier to connect all the wires to the circuitboards first). The power amplifier boardwas fitted to the metal base plate of ourcase using the angle on which the tran-sistors were mounted. It was positioned sothat it fitted neatly between the two bat-teries in the bottom of the case. Togetherwith the loudspeaker, the amplifier boardholds the batteries without any furtherhelp.

The small loudspeaker for this pro-ject was mounted on the plastic case of thebox through which a number of holeswere drilled to let the sound out. If re-quired, a small mains power unit capableof 9-0-9 V at 100 mA or more may be usedto power the unit.

A foot pedal control for controllingthe wah wah effect could be plugged intoa jack socket. This would need to be oneof the three -connection or stereo type sothat positive and negative supplies as wellas the control signal could be connected.


VIC-20High Res GraphicsJ. EnnisThe recommended way to create high-resgraphics on the VIC-20 is to bit -map asmuch of the screen as you have memory for.But even with memory expansion cartridges,the maximum size is about 160 by 160 pixelsbecause character memory cannot be locat-ed in the expansion cartridge.

The following program does not try tobit -map the entire screen, so it avoids thislimitation. When plotting graphs and thelike, only a small portion of the screen is ac-tually used.

To turn on a single pixel, the programPEEKs into screen memory at the place thepixel will appear when it is plotted. If thecharacter there is a space, it POKEs anothercharacter in its place and then POKES intocharacter memory to turn on a single dotwithin that character.

Thus, when a graph is plotted, most ofthe screen is filled with spaces and the re-mainder with other characters.

Within the program the plotting ofpoints on the screen is achieved by twomachine -language routines which must bePOKEd into memory before running. Thefirst of these clear out the character memoryin RAM, sets the character memory pointerto 5120 (decimal), clears the screen and setsthe 8116 character size.

The second routine plots a point whosex and y co-ordinates are stores in locations 0and 1 respectively. Both routines are re -locatable but only work on the unexpandedV1C-20, although they could be modified.

Type in Program 1 and save it immedi-ately, taking special care with the data state-ments; a mistake there may well crash theprogram later. Erase the first program, thentype in Program 2 and save it on tape im-mediately after Program 1.

To use it, load and run Program 1,which POKEs the machine language intomemory; unless there is a mistake, it willthen automatically load and run the secondprogram on the tape, the one that does theplotting.

When run as above, the second pro-gram will plot the graph, in Cartesian co-ordinates, of a function defined in line 5. Todo this, it will ask for the domain of thefunction, i.e.: the range of values on the

x-axis for which values of the function are tobe plotted.

It will then ask for the plotting density,i.e.: how close together it will plot thepoints, where 1 gives the highest density and4 the lowest.

Once plotted, the graph will remain onthe screen until the user presses the CTRLkey and then the space bar.

Both parts of the program should betyped in without any spaces between wordsas this saves using too much memory space.

MACHINE -LANGUAGE GRAPHICS Program 1

10 REM LOAD`.' MACHINE -LANGUAGE20 CH=0:FORI=5892T06119: EADA:POKEI,A:CH=CH+A:NEXT:IFCH033481TRENPRINT"ERROR":END30 FORI=5892T06119:POKEI-1000,PEK(I):N=AT:POKE631,131:POKE198,1:END40 DATA173,3,144,9,1,141,3,144,169,8,141,15,144,169,253,141,5,144,169,147,32,210,25550 DATA169,0,133,251,169,30,133,252,169,150,160,n,145,251,200,192,0,208,249,230,252,16560 DATA252,201,32,208,237,169,20,133,252,169,0,133,251,160,0,145,251,200,192,0,208,24970 DATA230,252,165,252,201,30,208,235,96,169,0,133,2c0,133,252,133,253,133,254,165,080 DATA24,105,248,230,251,176,249,198,751,165,1,74,105,240,230,252,176,249,198,252,16690 DATA252,169,0,24,105,22,202,224,0,208,248,24,101,251,133,753164,253,185,0,30,201100 DATA150,208,9,173,255,29,153,0,30,238,255,29,133,253,165,1,166,252,56,233,16,202110 DATA208,250,133,254,169,20,133,3,165,254,166,253,24,1P5,16,144,2,230,3,202,224,0120 DA'A208,244,133,2,165,0,166,251,56,233,8,202,224,0,208,248,133,252,169,7,56,229130 DATA252,170,169,1,24,133,251,101,751,702,224,0,208,246.135,252,201,0,208,2,230,252140 DATA160,0,177,2,5,252,145,2,96

Program 2

5 DY.F":';A(X)=SIN(X)10 POKE36878,9:PRINTCHRS(147)SPC(48)"VIC GRAPHICS":PRINTSPC(90);:INPUT"DOMAIN(A,B)";A,B20 IFA>=B7HENPRINTSPC(50)"ERROR":POKE36876,200:FORT=0T01500:P0KE36876,0:GOT01030 PRINTSPC(45);:INPUT"PLOT DENSITY(1-4)";O:IFC(10R0)4THENC=440 SYS4892:PCEE7679,1:D=C*(B-A)/175:U=0:L=0:FORI=ATOBSTEPD:C=FNA(I):IFC(LTHNL=C50 IFC>UTHENU.060 !I7XT:H=175/(ABS(L)+U):W=175/(B-A):IFB(0 ORA>OTREN8070 POKE0,-A"W:FORI=OT0175:PMKE1,I:SYS4968:NEXT80 POKE1,175-Air(L)*H:FORI=OT0175:POKEO,I:SYS4968:TTXT90 PORI=ATCBSTEPD:C=FNA(I):X=(I-A)*W:Y=175-(ABS(L)+C)*B:POKE0,X:POKE1,Y:SYS4968:NEXT95 P0KE36875,180:FORT=0T0600:NFIT:P0KE36875,0:WAIT653,4:WAIT197,32100 P0KE36879,27:POIE36869,240:POKE36867,PEEK(36867)AND254:POKE198,0:GOT010


1

2

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Cards80 Column CardDrive CardZ80 Card16K RAM Card6502 Motherboard (bare)Any (bare) Card

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Book ReviewMathematics for Electricity/Electronics

Miller/Culpepper, Collier MacMillan Can-ada Ltd., ISBN 0-02-818220-0. Paperback.ALTHOUGH THIS book is intended foruse in an electronics course, it's an excellentchoice if you'd like a reference book of basicinformation and equations. For instance,who can remember Delta -Wye transformsunless you use them daily? With this handymanual, you have the information youneed, and wonder of wonders, it's all easy tofind, thanks to excellent layout.

The book is divided into 30 chapters, orunits. Each unit consists of an introductionto the basic topic, relevant tables and testproblems for the eager. The main formulasare placed in boxed inserts for readability.The answers to the tests, unfortunately, arein a softbound book which must be pur-chased separately; after all, it's meant to endup in classrooms, and we can't have peoplepeeking.

Taking the first unit, Resistance, as anexample of the format, you'll find a one -page discussion of the various factors affect-ing the resistivity of conductors. Two pagesof tables and examples follow; the tables in-clude the determination of the resistance ofa material given the dimensions, the effectsof temperature, and standard wire gauges.The examples are expertly concocted by so-meone who has the rare ability to put him-self in the place of the information -seeker.Seldom -used terms are neatly explained.There is a lack of metric units, for whichsome may breathe a sigh of relief, but natur-ally the book's largest market would be inthe U.S.

Problems accompanying each unit areof a practical nature; they describe the sortof situations one might be expected to findoutside the classroom: for instance, findingthe resistance of an electric clock coil giventhe length, wire, and temperature. You mayrarely need to know about clock coils, but ifyou wind any type of coils, say, speakercrossovers, you can appreciate the practical-ity of the approach.

Unit 2 applies resistivity using Ohm'sLaw. Three examples are given, along with25 questions. Interestingly, the authors givethe old high school rule -of -thumb for re-membering the Law: divide a pie into threeand cover the unit to be found; the othertwo are then shown in the proper relation-ship. The problem with this, as I recall from

MATHEMATICSFOR ELECTRICITY/ELECTRONICS

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MU FR /CULPEPPER

33.

high school, is that nobody can ever re-member which letters go in which sections ofthe pie.

The following units cover manipulationof series and parallel resistances, with Unit 6being particularly excellent at showing howto reduce complex resistor networks to easilyuseable equivalents. This should give a goodgrounding for later work in networkanalysis.

There are units on the basics of metermovements, and the ways to go about turn-

ing them into ammeters, voltmeters, orohmmeters. Kirchhoff s Laws and series -parallel current flow are covered in a simplebut concise manner; the authors have clever-ly managed to cram the equivalent of anelectronics course into three -page sections.(Quick. What are Kirchoff s Laws?)

Inductance formulas are given in twounits; you can even find formulas for wind-ing your own coils, should you be so eageras to actually do that. I used to pass onbuilding any project that required coil-wind-

68-DECEMBER-1983-ETI Continued on page 78

Parts PERIPHERAL CARDSIBM PCTMLOOK -A -LIKE CASE

Maice your Appletm or 6502 machine look like an IBMPC m. This attractive metal case with ABS front bezellooks just like you -know -who, but is punched internallyto take all the 6502 Mother boards, power supplies etcthat are now sold. Our black beauty power supply fits injust right with the power connector and switch ac-cessable at the right hand side. In addition the caseholds 2 standard disc drives (4 slim lines) with all holespre -punched. There is also a cut-out for a 41/4 inch muf-fin fan inside. Look at the photo, it really looks good

Keyboard Case $ 29.95

UNITRON 2200CASE

An attractive case and keyboard combination that givesthat modern look to your 6502 machine. The case fits theolder numeric keyboards and the PCB goes into thecase just fine. Comes in an attractive carrying carton.Case and KB case together $ 89.95Case only $ 69.95KB Case only $ 29.95Keyboard and KB case $119.95

UNITRON 2200PCB

A great new PCB, with Z-80, Disc controller, 64K and softswitch on board. Made to run with CPM systems underZ-80 control. Fits into the 2200 case above and use the2200 KB and case listed. Bare PCB $ 44.00

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Our ASCII keyboards are by ALPS, a famous Japaneseswitchmaker and feature high quality debounced swit-ches. Full upper and lower case capability. Direct plugin compatible with all 6502 boards and 'SURF' board.Available in numeric and std style.(a) Standard KB $89.00(b) Numeric KB $99.00

New low prices.

A) Z-80 Wired n tested ....$59.95..Bare PCB . $12.95B) 80 Col. Wired n tested ..$74.95..Bare PCB $12.95C) 16K Wired n tested ....$59.95..Bare PCB . $12.95D) Disc Wired n tested ...$69.95..Bare PCB $12.95E) Shamrock 13116 sector disk Wired n tested $79.95F) Appletm Prototype card, all WW holes $12.95G) Appletm Prototype card, power bussed $14.95H) Wildcardtm, Wired n tested.$59.95.Bare PCB $12.95I) 128K Wired n tested, no IC's $69.95

With 64K .$149.94, 128K .$239.95, PCB $24.95J) IBM PCtm Prototype board, WW only, has a DB-25

footprint and a DB-9 footprint on end for I/O, all theremaining area is WW holes on .1" $34.95

K) IBM PCtm Memory prototype board, same as abovebut a 256K/1024K memory (for 4164 Or 41256 IC's)has been laid out at the inboard end with all the bitsbussed as 4 separate banks of 64K/256K with parityand babk select isolated, saves a lot of work in WWmemory design $44.95

L) IBM PCtm Mother board, a powered 6 slot Motherboard that allows the use of our CP I/O 8088 plus ourmonochrome video/memory board to make a fullyIBM compatible system. Note this is a 62 pin bussedMother board similar to S-100 Mother boards in con-cept, it thus allows you to plug in any IBM peripheralboards to make your own PCtm clone along with ourCPU board $34.95

M) IBM PCtm Our newest and most exciting product forthe PCtm market. Our designer looked at the pastsuccess of the S-100 design and took apart an IBMPC and relaid it out as two standard IBM plug incards. One is the main CPU with Disk Controller I/O,8087, 8088, keyboard I/F onboard and the other is astd monochrome video board with 256K of memory.The ROM bios has been completely rewritten so asnot to infringe any IBM copyright and since theBasic and DOS are available on the legal market,you can make a fully compatible system that is alsofully legal software -wise.SEND FOR COMPLETE DETAILSPrice ...Main CPU board, wired n tested $695.00

Video board, 64K $475.00128K $545.00192K $625.00256K $695.00

Power supply, our new power supply is not readyyet, however the black beauty power supply will runa minimum system with 2 standard floppy drives.

N)

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Our Famous "BLACK BEAUTY" power supply, nowreduced in price but not in quality. Our ratings are 5V -5A;12V -2.5A; -5A-'/,A; -12V-1/2A for real. Make sure that anyother power supply that lays claim to this rating actuallydoes so. Labels are cheap and we have seen many of theold silver power supplies unchanged except for thelabel. Easily beats all the rest $99.95

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THE GREAT DEALCARRIES ON FOREVER AND GETS BETTERWe made an even better buy on over 1000 sets of powersupply, 6502 board, numeric keyboard and numeric ABScase (solid coloured ABS All the way through, not justpainted plastic) and can now offer the great deal withnumeric case and keyboard for the amazing price of

$275.00along with any 4 of the peripherals listed above as abare pcb with parts layout. The price is the same fornumeric or non -numeric styles of KB and case for thisgreat deal. Please specify numeric or non -numeric whenyou order, Except 128K, wildcard.

ri41111111

SYSTEMSAVIOUR

Hot and getting hotter??? Got an older power supply???Then you need a SYSTEM SAVIOUR. This is not areligious object, it is a nicely packaged 31/2" muffin fanin a molded plastic housing that fits against the slots onthe side of our 6502 computer case and draws out thehot air. Widely used by all major political parties,especially the NDP, now at a new low -low price. Com-plete with 2 grounded 3 wire switched sockets, pilotlight, surge protector and on -off switch to turn off yoursystem and two plugged in items $55.95

MAIL ORDERSWe accept; Personal Cheques, Postal Money Orders,Certified Cheques, Travelers Cheques, Visa, AmericanExpress, Mastercard, Bank Draft. We ship C.O.D. only byCANPAR and Truck. We do not use Canada Post C.O.D.We will send your goods via CANPAR or Canada Postunless you say otherwise. You will be charged a min$3.00 for delivery and handling or more if your goods areheavier than the $3.00 weight or if you specify anotherdelivery service that charges more. All Ont res + 7%sales tax. We sell wholesale to any retail store or otherreseller with a sales tax exemption U. as long as arealistic quantity is bought. We ship within a week if instock and we will cancel any backorders over 4 weeksunless otherwise instructed. 20% Restocking Charge.


Canada's PersonalCam acting Magazine

December 3

el ACASHFLOW ov

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5288 5288 5

5288

INSIDE IBM Clones Echo H Review

Birth of a Dialing Terminal Pied Piper Review Accounts on a Computer And More . .

December Issue on sale nowat your newsstand and at 100

computer and electronic storesacross Canada

Save up to 47% by subscribing. One year (12 issues) $19.95, two years (24 issues)$34.95. Send to Computing Now! Subscription Department, Suite 601, 25 Overlea

Blvd., Toronto, Ontario M4H 1B1.

L J

Two wires for opto-switchF. Arfort

L

Here's a simple way to run two wires in-stead of four to a remote opto-switch, asin the case of a wind speed indicatorwhich provides pulses proportional to therotational speed of a perforated disc.

An opto-coupler consisting of a LEDand a phototransistor, either of thepackaged variety or made from discretedevices, normally requires four connec-tions. However, twin -pair cable is com-mon, cheap and convenient and it's moreeconomical (and more elegant) to use twowires rather than four for a remote sensor.The further away the sensor may belocated from the indicator, the more at-tractive a two -wire system becomes.

In the circuit, resistor R1 provides a`starting' current for the LED. Currentthrough RI and R2 will provide a certaindc level at the output when the path bet-ween the LED and phototransistor isblocked. When the path is unblocked, thephototransistor saturates, virtually shor-ting out RI, thus providing more currentthrough R2, increasing the output dclevel. This change can be sensed and usedas required.

Fuse fail indicatorR.N. SinclairThis circuit indicates an open circuit fuseby flashing the LED D I .

The circuit is based around thepopular 555 timer IC which is arranged asa multivibrator with its frequency/perioddetermined by Cl, R3 and R4. R1 is thecurrent limiter for DI.

When the fuse is intact, the BC558 isoff but when the fuse fails and there is anopen circuit the BC558 switches on, sup-plying power to the input of the 555 (pin

J0

1). A load must be present to switch thetransistor on and consequently the LED.

The fuse fail indicator must not beused when the power supply is greaterthan 15 V.

AffordablePrecision

Arkon is now handling the Hitachi line of high-performance digitalmultimeters. These precision instruments are able to meet the moststringent requirements of both engineer and hobbyist, yet fit comfortably inthe palm of the hand and are easily transported.

In addition to these meters, Arkon also carries the complete line ofHitachi scopes and other test equipment by such manufacturers as Hiokiand Lutron. In stock as well is a good selection of components includingsemiconductors and ICs, kits, tools, and manuals. Everything that's neededto get the job done.

Make it a point to drop by soonfor a demonstration, or visit us atthe Home Entertainment Fair, booth124, from December 8 to 11.

Hitachi

Circle No. 5 on Reader Service Card.ARKON ELECTRONICS LIMITED409 QUEEN STREET WESTTORONTO M5V 2A5 (593-9653)


Tech Tips

220v16V

STANDARD CEILING ROSE

LOAD250WMAX

NOTE.ICI IS 555PIN 7 IS NOT CONNECTEDQ1 IS 8C337, ZTX300 ETC.SCR1 IS TIC 206ZD1 IS 12V ZENER

LAMP

TYPICAL CONNECTION SCHEME

SELF-SUFFICIENTEPROM COPIER/PRO-GRAMMER

Includes its own Z80 -A processor Needs no personality module Copies: 1, 2, 4 & 8K bytes single supply EPROMs Comes with a powerful 4K bytes monitor

ONLY $99.00 (kit)

With this KBH interface, youcan modify your EPROMcontent or load a new code inthe PRO-GRAMMER's RAMbefore transfering onEPROM. You can also accessseveral operation modessuch as: Memory and register

examine and change Insert/delete one or many

bytes anywhere in a pro-gram

Break point executionmode

Block transfer mode and much, much more

ONLY $59.00 (kit)

FREECall or write for your free copy of the products

catalogue manufactured byPROTEC MICROSYSTEMES INC,

725 Decarie Suite 202, St -Laurent, Que. H4L 3L4(514) 744-3363.

Add 3% shipping and handling, Quebec residents: add 9% P.S.T.Cheque, money order, visa accepted. Please print your name, visa no,expiration date 8 signature.

Low -Cost Mains Time -Delay SwitchAlex Gray

This circuit offers a cheap, reliable replacement for mechanical andpneumatic time -delay switches such as used for corridor lights. It can alsobe used to protect equipment which is upset by power being applied andremoved too rapidly.

When the switch is closed and reopened, the load is switched on for apreset time - 1.112,C. During this period, the circuit also switches on its ownpower. At the end of the time -delay both the load and the circuit aredisconnected. In the event of a circuit failure, the push button will stillallow the load to be switched on for safety (e.g. in corridor lighting).

If the switch is a normal latching type, the load will be powered as longas the switch is closed, subject to a minimum period. This prevents rapidcycling of the power on and off and may be used to protect equipmentsusceptible to damage from this situation.

The usual precautions with AC wiring must be observed. In particular,remember that, although the 555 is on a 12V supply, that supply is superim-posed on 120 V AC above ground. The switch and the 470nF capacitormust be types designed for high voltage operation.

Reuse spent solder braidPeter Alter

USED BRAID USEDSPAGHETTI BRAIDINSULATION

Don't throw away those used pieces of Dri-Wick or other brands ofdesolder braid. It is an excellent, very low resistance conductor.

It can be used as a ground strap from circuit boards and connectors tothe chassis or central earth point. Covered by spaghetti or heat shrink tub-ing, it makes an ideal low impedance lead for power supplied andamplifiers etc.

It has much lower resistance than hook-up wire, doesn't cost anything,and being rigid makes a good supporting strengthener for the pc board.



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CLASSIFIEDADVERTISINGETI's classified advertising sectionallows you to reach about 30,000Canadian readers nation-wide for $1.00per word. For as little as $20 per inser-tion (there's a 20 word minimum) youcan promote your business from coast -to -coast.

WHAT DO YOU DO?Send us your typewritten or clearlyprinted words, your permanent ad-dress and telephone number and yourmoney (no cash please). Make your

cheque or money order payable to 'ETIMagazine'. We're at Unit 6, 25 OverleaBlvd., Toronto, Ontario, M4H 1B1.

WHAT DO WE DO?We typeset your words (and put thefirst word and your company name inBOLD capital letters). If we get yourmessage by the 14th of the month, itwill appear in ETI 11/2 months later. Forexample if we receive it by October14th you (and thousands more) will seeit in the December issue.

DIGITAL ORGAN KITS for sale. Demo LP($8.00) and free brochure available fromSELTRON INSTRUMENTS, 35 SouthbridgeSt., Leamington, Ont. N8H 4N4.

SATELLITE T.V. project July, Aug., E.T.I.Hard to get parts, Ga As Fets, microwave P.C.board, LNA's downconvertors, dishes etc.Send S.A.S.E. to COLESAT SYSTEMS,RR#2, Tantallon, N.S. BOJ 3J0.

DIGITAL interfaced DC motor speedcontrol.8bit in, DC out at up to 20amps. Great forrobots and automation with micros. SERVO -AMPLIFIERS INC., P.O. Box 568, Station A,Toronto M5W 1E4.

PLANS to build your own backyard satellitedish and pay -TV decoders. Send a S.A.S.E. to:J.C. SYSTEMS INTERNATIONAL, Dept.306, 7305 Woodbine Ave., Markham, Ont.L3R 3V7 for free information.

TI -99/4(A) OWNERS! - Original games oncassette. Send for free list. GIGO SOFT-WARE, Box 673, Niagara Falls, Ontario L2E6V5 Canada.

SAVE money on breadboard, LED's, resistors,multimeters and much more. Send for yourfree flyer. P & 0 DISTRIBUTORS, P.O. Box1293, Stn. E., Victoria, B.C. V8W 2W3.

PRINTED CIRCUIT BOARDS for ETI andHam Radio projects. NDFL Amplifier - $6.70;Green house sprinkler - $4.65; Noise ReductionUnit - $4.10; Spectra Column - $7.85; PrecisionPulse Generator - $9.50. Full list free. Boardsfrom ARRL Handbook 1983 available. Postand pack $1.00, Ontario tax 7%. B -C -DELECTRONICS, P.O. Box 6362, Sta. F.,Hamilton, Ontario. L9C 6L9.

APPLE -CLONE CIRCUIT GUIDE. Fullschematics, waveforms and tutorials. Essentialfor servicing, and interfacing. $18.95. IN-TERACTIVE MICROTRONICS, Box 358,Pinawa, Man. ROE ILO.

DID YOU BUY THE WRONG COMPUTER?We buy and sell used and new computers. Wehave one of Toronto's BEST Technologists onstaff. Fully equipped computer service onpremises. APPLE types our specialty!GENERAL ELECTRONICS, 5233 Yonge St.,Willowdale, Ont., (416) 222-3626.

6502 System Computer, 64K memory, multi-function numeric keyboard, upper -lower case,with 12" green monitor, 1 disk drive with con-troller, Z-80 card, Apple= and CPMtm soft-ware compatible. All for $1250, shipping in-cluded. Send certified cheque or M.O. Ont.Res. add 7% Sales tax. APL MICROWARE,P.O. Box 21, Oakville, Ontario L6J 4Z5.

COMPUTER programming aid -A 16 bitDec/Bin/Hex slide convertor $3.75 ea. R.HARDER, 995 Shakespeare Ave., North Van.,B.C. V7K 1E7 ($16.25 for 5 cony).

SPECIAL Resistors - 100/$1.00; Capacitors- 20/$1.00; Diodes - 15/$1.00; Transistors- 15/$1.00; list - products & kits - $0.50 forpostage. All orders add 10% for P/H, Ont.res. add 7% p.s.t. Send orders to: ELECTRONCOMPUTERS, P.O. Box 613, Stn. `U',Toronto, Ontario M8Z 5X9.

PORTABLE AM and FM Booster Antennas.Tested speakers, surplus tubes and other radioparts. List/order from: ELDON ELEC-TRONIC ENTERPRISES, 10653 - 137AStreet, Surrey, British Columbia, Canada V3T4J7.

AMAZING Electronic Projects and Devices.Ultrasonics, hand held disrupters, repellors,lasers, battery pocket sized, high-powered,tesla coils, force fields, atomic, surveillance,mini -transmitters, plus much more. Catalog$1. Mail orders only. DUKER ENTERPRISES8932 - 155 St., Edmonton, Alta. T5R 1W4.

INDUSTRIAL CONTROL COMPUTER.8085 based, on board Eprom, RAM, RS232,power supply. Able to upload, download dataor programs from host or development system.26 I/O lines, 16 of them buffered for 500ma/at35V DC. Bare board + doc. $39.95, completekit $115.00, Ass. + tested $140.00. ELEC-TRONIC SPECIALTIES, 7794 Kittridge Dr.,Mississauga, Ont. L4T 3J6.

6809 with 64K, 2 serial and 2 parallel ports, 5"DS/DD floppy controller, on 2 Eurocard-sizeboards. Write for brochure. SARDISTECHNOLOGIES, 2261 East 11th Ave., Van-couver, B.C. V5N 1Z7.

RADAR detectors (both bands), descramblers(sync., inverted video and variable), phasors,lasers, surveillance equip., satellite dishes, andlots, lots more. Catalogue $2 refundable. Nocheques. F.T.S. ELECTRONICS, Box 574,Brantford, Ont. N3T 5N9. Same day service.

ZX81 Interface kit, featured in April ETI$34.95. New low prices on following items. Ex-pander for experimenters, adds two 22/22/.156and one 23/23/.1 connectors to theTimex/Sinclair buss $19.95. Also ZX81 videoamp, adds composite video output $4.95. Add$2.00 P&H each order. JDC 5-14 Sentinel Rd.,Downsview, Ont. M3M 2Y5.

ZX81-TIMEX 1000. Word Sinc II. Profes-sional word processing with ZX or TimexPrinter. Print 42 UPPER and lower case lettersper line. 20 special characters. Typewriterkeyboard, all keys repeat. 60 wpm typingspeed. Full screen editing. Text justification.Commands to: page; list; delete; move;replace; tab; expand print. Super fast flickerfree machine code. Exceptional program.$19.50. Super Data Save, Save Verify andLoad named programs, or Data Files, at 14times Sinclair speed. Many additional features.Comes with superior filter and manual. Almosta disk drive. $54.25. Tactile FeedbackKeyboard Overlay, Feel your keys. $4.50. P.HARGRAVE, Site V, RR 4, Nanaimo, B.C.V9R 5X9.

SCANNER Crystals, $7.50 each state freq. andmake. B.C. Freq. Manual $10.00. PartsGalore; Educational Kits. Cat. $2.00. Allow6-8 wk. delivery. GLENEAGLES ELEC-TRONICS, 1896 Springhill Dr., Kamloops,B.C. V2H 5J3. Phone 372-9604.

EXPERT services offered in Micro Electronicsdesign, PCB layout and stuffing with quickturnaround by: PERPETUAL MOTIONSENT., 2643 Kennedy, Scarborough M1T 3H5,293-4864.

SURF Board owners, now you can have detail-ed service schematics. Send $20.00 certifiedcheque or M.O. payable to G. STYRNA, P.O.Box 13055, Kanata, Ont. K2K 1X3.

SEND me $2.00 for Christmas, I'll send youmy catalog with Timex Sinclair Computers.COMPUTER SOURCE CENTRE, P.O. Box3637, Station A, Ottawa, Ont. KIY 4J7.

STUDENT discounts on resistors, capacitors,I.C.'s, semiconductors. Pick up your freeHOBBILT catalogue at the store: 7454Langelier, St. Leonard. Tel: (514) 259-5581. Ormail your name and address to HOBBILTELECTRONICS, 7303A Dumesnil, St.,Leonard, Que., HIS 3A7.

HAS your DMM or Frequencymeter TALKEDTO YOU lately? If not, then you need FRE-QUENTALKERTM! Imagine: you don't haveto look up while measuring. It tells you in plainEnglish what's on the display. Easy interfacingto any digital equipment (please specify withorder). Send $129 to microNOVA ELEC-TRONICS, P.O. Box 1284N, Halifax, N.S.B3K 5H4.


APPLETm-builders need "APPLE -SEED"!Comprehensive step-by-step instructionmanual for assembling your microcomputerkit. 60 pages, 70 illustrations. Send $9.95 (in-cludes postage) to: NUSCOPE ASSOCIATES,P.O. Box 742, Stn. B, Willowdale, Ont. M2K2R1. Quantity discounts.

COMMODORE 64 owners. We offer a fineselection of programs. Send for free catalogue.SANDISON SOFTWARE, Box 1403,Chatham, Ontario, N7M 5W8.

MULTIFLEX owners: Screen orientedoperating system, editor and software develop-ment tools for Z80A system. Canadian madevideo terminals also available. ZEMOSSYSTEMS LIMITED, 7225 Woodbine Ave,Suite 110, Markham, Ontario L3R 1A3.

CORONET ELECTRONICS, 649A NotreDame W., Montreal, Que. H3C 1H8,Catalogue IC's, Semi's, Parts, send $1.00 tocover postage. Monthly specials at crazy prices.

TIMEX-SiNCLAIR Software and Hardware.Brand name products at incredible prices! Sendfor FREE catalogue -price list. TORONTOSOFTWARE WORLD, Box 84, Dept. E,Agincourt, Ontario. MIS 3B4.

HYDROGEN GAS GENERATOR plans andstarter kit, $12.PRAIR1E POWERRESEARCH AND DEVELOPMENT, P.O.Box 8291, Edmonton, Alberta. T6H OLO.

NEW catalogue of components available. Geton our mailing list for regular bits and bytesspecials. M.O. ENTERPRISES, Box 2066E,Bramalea, Ontario. L6T 3S3.

J&J ELECTRONICS Ltd., P.O. Box 1437E,Winnipeg, Manitoba R3C 2Z4. Surplus andSemiconductor Specialists. Do you get ourbargain flyer? Send $1.00 to receive the currentliterature and specials and to be placed on themailing list for future publications.

WSI RADIO - SWL Radios - Ham radios 18Sheldon Avenue North, Kitchener, OntaricN2H 3M2. Tel. (519) 579-0536. Write for 1983catalogue, $2.00 (VE3EHC).

VIC20 owners! - Say goodbye to 'OUT OFMEMORY' messages! Memory Module 16Kfor $59; or expand your system to its full RAMcapacity with Module 32K for $99. Send tomicroNOVA ELECTRONICS, P.O. Box1284N, Halifax, N.S. B3K 5H4.

Tech Tips

Etching tankN.F. BushA discarded plastic bottle is a simple, buteffective, etching tank.

I was recently making up several pcboards and found that I did not have asuitable etching tank. The containerswhich I have used on other occasions wereflimsy and etchant was always spilt allover the place. So I grabbed an old bottleand cut it out as shown on the diagram.

I was amazed at how successful it wasas I could move it around and didn't spilla drop.

The used etchant can be discardedeasily by unscrewing the lid and pouring itout. There's not much mess to clean upafterwards and the bottle can be washedthoroughly and stored until needed again.

11/10.011.1E

111111111\.nUMW" FOINIC [MOW.

OM LOY 1.

llllllllll me llllllllllllllll mummummimmemmi Ill

Flashlight CommunicatorChris McRaeThis simple, portable, visually -alignedtransceiver is quite effective and can beeasily built into a flashlight.

The lamp current, modulated at anaudio frequency, modulates the lightbeam. The light beam is detected by aphotodarlington transistor and drives asmall speaker for audio output.

The lamp is driven by an ac signalwhich cuts the RMS voltage to about one-third of the six volts, which is why a 1.5 Vbulb is used in a 6 V circuit.

The photodarlington can be mountedon the axis of the beam or you may getbetter sensitivity by placing it so that itfaces the reflector of the flashlight justabove the bulb (the bulb filament is at thefocal point of the reflector).

Fidelity is not high due to the lowpass characteristics of the bulb filament,but I have been able to have intelligibleconversations at distances up to 30metres.

llllllllll 11111111111111111111111111111111111111111111111111I llllll

Quality Boards & Kits APC -1000 Basic on your command

$- 650.00

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cap lock

11 Apple" Compatible128K RAMCARDSoft -warenot included.Christmas Special $195.00

PC -5500 64K PERSONAL COMPUTER 188 FUNCTION KEY

10 USER DEFINE KEY(KEEP MEMORY 5 YEARS)

DISK DRIV EXCLUDED. $850.00

New 6502 Mark IV64K RAM plus built in Z-80

*Dkk Controller Card ***Micro Modem Card*80 Column Card ***80118 Card*New EPROM Programmer Crd**6809 Card*New RAM Card **A/D D/A Card

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Price for above PCB *SI0.00 ea., *$15.00 ea.,***525.00 ea., kits also available.

JOYSTICK MINI FAN 3M DISKETTE DISKETTE STORAGE BOX HEAD CLEANING

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Terms: Send cheque or money order (allow 2 weeks for per-sonal cheques). Credit cards wekome. No C.O.D., QuebecRes. add 9% sales tax. Min. order $10.00. Add 5% for ship-ping and handling, except Case & Power Supply. 20%restocking fee for returned merchandise. Prices andavailability subject to change without notice. Do not sendcash.

Dealers InquiryWekome

FUJICOMP INC.6420 Victoria Ave., Suite 3,Montreal, Quebec. H3W 2S7

Tel. (514) 733-5612



Brother EP -20 Electronic Typewriter

maias "g" or "y", or letters with descending accents, will ride up a bit higher than the rest. On theother hand, a 5 x 7 print head keeps the cost down.

CalculatingIn the upper right corner, you'll find five buttons marked with the usual calculator func-

tions. A typewriter with a built-in calculator? So it is. As you're typing up a storm, you can dofour -function calculations up to 12 digits and print them along with the text. If you just want tocalculate without actually printing it, you can switch to the non -print mode. There's a Clear keynext to the LCD readout, but it has to be used with care, because it likes to print out the con-tents of the buffer before clearing the display. The delete key can be used to get rid of unwantedcharacters if you've been calculating and don't want numbers printed.

Other features include a Repeat key which repeats the last character entered, includingReturn and Backspace, which have auto -repeat anyway. The Tab and Margin functions are setelectronically; just space to the desired point and press a button. Up to 16 tabs can be set. Thereis no visual indication of where the margins or tabs are located.

SummaryA number of people, including other reviewers, have said that while the EP20 is an in-

teresting toy, it has no real uses. I didn't find this at all. Here are the reasons I have one:First of all, for the same price as the average electric, you get the 16 -character correction

feature. This may not sound like much, but I've found that the main reason I use a word pro-cessor is to be able to instantly correct typing errors as the happen; it would be nice to be able tomanipulate text, but that's unlikely to be available for the price.

Secondly, the machine is easily portable and fits in a small space. I've never really wantedto type on a bus or airplane, but I like being able to slide the typewriter into a bookcase whendesk space is needed; you can't easily do this with most portables.

Thirdly, the EP20 is virtually silent in operation. This means that you can type late at nightor when someone is listening to the stereo.

On the negative side, there's the high cost of replacing the ribbon cassettes. Brotherhas a thermal paper available which eliminates the need for a ribbon, but the thermal quali-ty isn't up to the excellent quality of the ribbon printout. The return function is very slow,presumably to reduce strain on the tiny motor; this wasn't a serious drawback. I wasn't tookeen on the smoked acrylic print head cover; it tended to obscure the text for quite a fewlines, and you couldn't leave it off because the platen rollers are incorporated into it.

But these points don't detract from the fact that the EP20 is one of the best applica-tions of microcircuitry I've seen in a long time; it's a pleasure to own and use one.

"I'm so glad I found a bank that still gives personal service. I hatethose impersonal automatic tellers."

Where to BuyFLUKE

Digital /AnalogMultimeters

Fluke 70 Series Digital/ Analog multimetersare available in Canada through the Jet Stockprogram of Allan Crawford Associates Ltd.,or from the following distributors:Vancouver, B.C.

R.A.E. Industrial Electronics Ltd. 291-8866Instrument Service Laboratories Ltd. 278-4511

Victoria, B.C.Queale Electronics Ltd. 388-6111

Nanaimo, B.C.Queale Electronics Ltd. 758-8166

Vernon, B.C.Interior Electronics Ltd. 545-2394

Kelowna, B.C.Interior Electronics Ltd. 860-0585

Kamloops, B.C.Interior Electronics Ltd. 374-5002

Edmonton, Alta.Cardinal Industrial Electronics Ltd. 483-6266Instrument Service Laboratories Ltd. 463-7488

Calgary, Alta.Cardinal Industrial Electronics Ltd. 259-6817

Regina, Sask.Radio Supply & Service Ltd. 352-8642

Winnipeg, Man.Wes Electronics Ltd. 632-1260

l.ondon, Ont.C.M. Peterson Co. Ltd. 434-3204

Toronto, Ont.Electro Sonic Inc. 494-1555C.M. Peterson Co. Ltd. 247-5437Armatek Controls Ltd. 251-3111Transmation Canada Inc. 675-5980

Peterborough, Ont.Weesco-Peterborough 745-2493

St. Catherines, Ont.C.M. Peterson Co. l.td. 685-7377

Kitchener, Ont.C.M. Peterson Co. Ltd. 745-0981

Sarnia, Ont.C.M. Peterson Co. Ltd. 344-3382

Windsor, Ont.C.M. Peterson Co. Ltd. 253-1161

Hamilton, Ont.C.M. Peterson Co. Ltd. 528-0151

Thunder Bay, Ont.C&F Electronic Distributors Ltd. 345-6515

Sudbury, Ont.Sonic Northern Ltd. 674-0764

Timmins, Ont.Sonic Northern Ltd. 264-1228

Sault Ste. Marie, Ont.Sonic Northern Ltd. 254-1418

Ottawa, Ont.Electronic Wholesalers Ltd. 746-4413

Montreal, Que.Electronic Wholesalers Co. Ltd. 769-8851Franklin Electric Canada Ltd. 341-6260

St. Jean, Que.Produits Electroniques en Gros

(St. Jean) Cie. Ltee. 348-4961Chicoutimi, Que.

Franklin Electric Canada Ltd. 545-8313Noranda, Que.

Simtronique Inc. 762-1874Halifax/Dartmouth, N.S.

Weesco-Maritimes 465-3730St. John's, Nfld.

Rideout Tool & Supply Ltd. 745-2240


lat Allan Crawford Associates Ltd.Test & Measurement Division

Toronto: (416) 678-1500 Montreal: (514) 731-8564 Ottawa (613) 722-7682Halifax: (902) 463-8640 Vancouver: (604) 294-1326 Calgary: (403) 230-1341

Edmonton: (403) 451-4893

The Digitalvs. Analog

battle is over.

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Mathematics for Electricity/Electronics

ing. The section on peak/RMS follows. Theexplanation given here is not of the samecalibre as the rest; I can understand thereluctance to get into a subject requiring aknowledge of statistics sampling, but theremust be thousands of students and hob-byists who know only that peak equals RMStimes 1.414, or at best, the root of the meanssquared.

This brings up another interestingpoint. The root of two is shown in this sec-tion as 1.414, yet some of the examples inthe book have been worked out to eightdecimal places or more. This is an impossi-ble degree of accuracy, but on the otherhand, it lets you know whether or not yourcalculator is bang -on, or whether you've hitit by a lucky accident.

Inductive reactance, basic capacitance,and basic transformers are well -explained,and lead into eight units which are concern-ed with the characteristics of RC circuits.The beginning unit of these covers the RCtime constant. This one seemed to me tosum up even more than the RMS problem

the tightrope on which handbook authorsteeter: if you insert clarifying text, you mayget taken to task for overdoing things. Ifyou don't, people will say that the equationsare inadequately explained. With this inmind, I thought that there should have beena better explanation of why the mysterious63.2% keeps turning up in time constants.At some point, the student will likely stum-ble across the fact that it derives from e, thebase of the natural logs, but it would be niceto have it spelled out.

Now we get to the fun stuff. If you canget the hang of capacitive reactance, you'reon your way to understanding impedances,and then it's only a step to complex circuitdesign. The author have wisely chosen thesimpler formulas which read out in ohms;for example, the RMS sum of reactance andresistance yields the impedance in ohms.Now, I'm not saying that the j operatorshouldn't be used instead; only that it'scumbersome, and delays being able to graspthe intuitive idea of impedance. Once youget the impedance concept stuck into your

head, it's only a matter of learning anynecessary equations. Until then, the studentmay only be parroting symbols withoutknowing why.

The book ends with units on series andparallel LC circuits; the format is the sameas those mentioned in the last paragraph.The appendices are jammed full of usefulinformation; some of it a recap of the unitsthemselves, and some of it additional.

This is a text that should be owned byanyone interested in electronics. The nega-tive points mentioned are, of course, a dif-ference of opinion as to how much supple-mentary text should be included in a refer-ence book. The superbly organized layoutmakes it a pleasure to use, and even stimul-ates the reader into doing more research ona topic. Oh, yes, I almost forgot. Mr. Kirch-hoff pointed out that voltage drops arounda circuit add to the supply voltage, and thatcurrent is the same in all parts of a seriescircuit. by Bill Markwick

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