Audiotel International Limited,

Operating Manual

PTX-12, PTX-22, VTXS-12, PTXS-22 TransmittersVRX-SL, VRXS-SL Receivers

Vehicle and AC Power SuppliesReceiver anct Telephone. Interfaces

Issue 2, January 1985

r

Should any problems arise or if further technicalsupport is required please contact:

Audiote l In ternat ional L imi tedCavendish CourtyardSallow RoadWeldon Industr ial EstateENGLAND NN17 1DZ

Tel : 0536-66677

Tlx: 341775 AUDINT G

Fax: (0536 66711)

Or contact your local supplier

C O P Y R I G H T 1 9 8 7 A L L R I G H T S R E S E R V E DThe contents of thispublication may not bereproduced wi thout thepermission of Audiote lIn te rna t iona l L imi ted

Contents

1.1 In t roduc t ion1.2 Scrambler Option1.3 An Integrated System1.4 Qua l i t y1.5 Technical Support1.6 Use of this Manual1.7 Guarantee

Section 1 - Overview

PiPiPip2p2p2p21 . 8 S e r v i c i n g p 2

Section 2 - Preparation for Use

2 . 1 U n p a c k i n g p 32 . 2 O p e r a t i n g E n v i r o n m e n t p 32 . 3 S t o r a g e a n d S h i p m e n t p 3

Section 3 - Common Aspects

3 . 1 C o n s t r u c t i o n p 43 . 2 B a t t e r y S u p p l y p 43 . 3 B a t t e r y U s e - T r a n s m i t t e r s a n d R e c e i v e r s p 53 . 4 C o n n e c t i o n s p 53 . 5 A n t e n n a s p 53 . 6 A n t e n n a P l a c e m e n t p 6

Section 4 - VTX-12 and VTX-22 Transmitters

4 . 1 I n t r o d u c t i o n p 74 . 2 C o n t r o l S w i t c h p 74 . 3 M i c r o p h o n e G a i n P o s i t i o n p 74 . 4 C o m p r e s s o r A c t i o n p 84 . 5 V O X O p e r a t i o n p 84 . 6 P T T O p e r a t i o n p 94 . 7 R e p e a t e r O p e r a t i o n p 94 . 8 R e m o t e C o n t r o l O p e r a t i o n p 94 . 9 T r a n s m i t t i n g T i m e s p 94 . 1 0 C o n n e c t i o n o f U s e r ' s A c c e s s o r i e s p l O4 . 1 1 S c r a m b l e r O p e r a t i o n - V T X S S e r i e s O n l y p l O

Section 5 - VRX-SL Receiver

5 . 1 I n t r o d u c t i o n p l l5 . 2 C o n t r o l S w i t c h p l l5 . 3 V o l u m e S e t t i n g p l l5 . 4 S q u e l c h S e t t i n g p l l5 . 5 O u t p u t S o c k e t p l 25 . 6 C o n t r o l o f E x t e r n a l E q u i p m e n t p l 25 . 7 R e p e a t e r a n d R e m o t e C o n t r o l A p p l i c a t i o n s p l 25 . 8 O p e r a t i n g T i m e s p l 25 . 9 S c r a m b l e r O p e r a t i o n - V R X S - S L O n l y p l 3

Section 6 - Vehicle Power Supply

6 . 1 I n t r o d u c t i o n p l 46 . 2 I n p u t p l 46 . 3 O u t p u t p l 4

pl4pl5

pl6pl6pl6pl6pl7Pl7

Section 8 ~ Receiver Interface Unit

8 . 1 I n t r o d u c t i o n p l 88 . 2 I n p u t s p l 88 . 3 O u t p u t s p l 88 . 4 F r o n t P a n e l C o n t r o l p l 88 . 5 A c c e s s o r i e s p l 9

Section 9 - VTX Transmitter Telephone Interface

9 . 1 I n t r o d u c t i o n p 2 09 . 2 O p e r a t i o n p 2 09 . 3 C o n n e c t i o n t o t h e T e l e p h o n e L i n e p 2 09 . 4 C o n n e c t i o n t o t h e T r a n s m i t t e r p 2 09 . 5 A u t o m a t i c R e c o r d i n g p 2 1

6.4 Ind i ca to r6.5 Accessories

Section 7 ~ AC P

7.1 In t roduc t ion7.2 Input7.3 Fuses7.4 Output7.5 Ind ica to r7.6 Accessories

1 1

Append ix A - VTX & VTXS Transmi t te r Spec i fica t i ons p22

A p p e n d i x B - V R X & V R X S R e c e i v e r S p e c i fi c a t i o n s p 2 4

A p p e n d i x C - Ve h i c l e P o w e r S u p p l y S p e c i fi c a t i o n s p 2 6

A p p e n d i x D - A C P o w e r S u p p l y S p e c i fi c a t i o n s p 2 7

A p p e n d i x E - R e c e i v e r I n t e r f a c e S p e c i fi c a t i o n s p 2 8

A p p e n d i x F - Te l e p h o n e I n t e r f a c e S p e c i fi c a t i o n s p 2 9Append ix G - Speech Scrambler Opt ion Spec ifica t ions p30

1 1 1

Section 1

Overview

1.1 Int roduct ion

The Audiotel VTX transmitters and the VRX-SL receiver have beendesigned to g ive excel lent per formance wi th great flexib i l i ty inapplications requir ing short-range, discreet communications.With the wide range of accessories and peripheral equipmentavailable a system is available to meet every possiblerequirement from long term room monitoring through to portableautomatic alarms.

Ready-made kits are available to suit the followingappl ica t ions:

Monitoring and recording of undercovermeetings (fixed and mobile)

Intelligence gathering through long and short termsurveillance of rooms and telephones

Monitoring of rooms barricaded or under siege

Protection of key personnel through two-way discreetcommunication

Noise and sensor activated alarms

1.2 Scrambler Option

The VTXS- and VRXS- series incorporate Audiotel's miniaturespeech scrambler module for protection against lower levelunauthorised interception. Transmitters and receivers can beswitched quickly between scrambled and normal operation.Excellent audio quality is retained during scrambler use.

1.3 An Integrated System

With the introduction in 1984 of the STX series of miniaturetransmitters and the VRX-ML high-performance multi-channelreceiver the range of applications has expanded further.All units within the Audiotel STX-VTX-VRX series are compatiblewith each other.

Interfacing with other Audiotel equipment is straightforward.All VRX receivers can directly control the Auto-cascade seriesof slow-speed (down to one-quarter of normal, giving up to 4hours of continuous recording per side of a C-120 cassette)cassette recorders.

1.4 Quality

Audiotel's products are designed and built in-house ensuringcomplete quality control. VTX transmitters and the VRX-SLreceiver both have type approval to UK standard MPT-1303.

1.5 Technical Support

Full technical support is avai lable to customers requir ingspecific or general information on the performance orapplication of equipment.

1.6 Use of this Manual

Operating instructions for the VTX transmitters, VRX-SLreceiver and peripheral equipment such as the vehicle powersupply have been included. Suggested applications beyond theobvious uses have been included.

Many operating characteristics are common to each unit withinthe VTX-VRX system and these are described in Section 3.

1.7 Guarantee

The equipment is guaranteed for a period of one year from thedate of original purchase. Please refer to our standard Termsand Conditions relating to claims under guarantee and return ofequipment. These are available on request.

1.8 Servicing

Equipment should be returned to Audiotel in the event of anyneed fo r se rv ic ing o r repa i r. I f th i s i s Imprac t i ca l thenservicing should only be carried out by qualified personnel.

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Section 2

Preparation for Use

2.1 Unpacking

The shipping container should be inspected for any damage. Ifthere is evidence of damage this should be retained until theequipment is checked and all accessories accounted for. Thiswill assist in any claims for damages due to transit.

2.2 Operating Environment

Specifications (see appendices) for equipment are applicable tothe following temperature and humidity ranges:

Temperature -10 deg C to +60 deg C

Humid i ty less than 95% re la t ive , non-condens ing

2.3 Storage and Shippment

When not in use the unit should be stored in a clean, dryenvironment. The permissable storage temperature range is -30deg C to +75 deg C.The original packing should be retained in case the unit needsto be returned to Audiotel. Before despatch of any equipmentto Audiotel the Sales department must be contacted. Theaddress, telephone and telex number are listed in the front ofth is manual . I f the or ig ina l pack ing mater ia l is not av ia lab lethen a sturdy airfreight quality carton together with generouscushioning material must be used. The carton should be markedclearly with the destination and the customer's name. 'FRAGILE'labels or markings should be attached.

Section 3

Common Aspects

3.1 Construction

With the exception of the telephone interface, the main chassisis formed by an extruded aluminium sleeve. All circuitry iscontained on a single circuit board. By removing the twoscrews on either side of the unit the sleeve may be removed.Power supplies must be disconnected before removing the sleeve.

Dismantling of units should only be carried out by qualifiedpersonnel.Access to the battery compartment and user-selectable optioncontrols where applicable are beneath the rear panel. Thispanel is retained by a single large-head 'coin-operated screw.

3.2 Battery Supply

With the exception of the telephone interface and the AC andVehicle power supplies units are powered by a single PP3battery. Alkaline types must be used as other types mayresu l t in fau l ty operat ion.

To insert a battery remove the rear panel by releasing the■coin-operated' screw. Gent ly pul l out the battery connectorc l ip and par t ia l ly inser t the bat tery wi th i ts terminalspoint ing away from the uni t . Whi lst holding the batteryconnect the c l ip . S l ide the bat te ry and c l ip fu l l y in to theunit. Tuck the excess leads around the top of the battery cl ipto allow flush fitting of the rear panel and screw.

Care should be taken not to cause excessive strain on thebattery leads.If the equipment is to be left unused for periods longer than amonth the battery should be removed.

3.3 Battery Use - Transmitters and Receivers

Batteries should be changed for each operation even if theprevious battery had only been used for a short period. Thiswil l prevent any confusion or doubts about the operating l i fe ofany battery.

Spare batteries are available from Audiotel.

3.4 Connectors

All accessories and peripheral equipment are connected viaself-latching plugs and sockets manufactured by Lemo. Spareplugs and sockets are available to purchasers of equipment fromAudiotel. Connection detai ls are given in each unit 's sect ionin this manual.

To connect multi-pin plugs align the socket and plug red markerpips and push the plug into the socket. The connector systemis self-latching to prevent disengagement by pull ing theconnecting cable. To release pull the barrel of the plug awayfrom the socket.

The VTX and VRX antenna connector operates on the same principleexcept that the orientation of the plug within the socket is notimportant.

3.5 Antennas

For many applications a flexible wire antenna is necessarythrough space and concealment considerations. Antenna lengthfor the VTX and VRX units is one quarter of the operatingfrequency wavelength. For example, if the operating frequencyis 150 MHz then the antenna length L is given by:

L = 1 / 4 x 3 0 0 / F F = 1 5 0

S o L = 1 / 4 x 3 0 0 / 1 5 0 = 0 . 5 m e t r e

Antennas supplied by Audiotel are pre-cut to the correct length,

50 ohm Coaxial extension leads and plug/socket adaptors can besupplied to meet individual requirements. Other antenna typessuch as magnetic mount and disguised whip types are available,please contact our Sales department for further information.

If the antenna is removed or short circuited to the chassisduring transmission no damage will occur to the transmitteralthough current consumption will increase.

3-6 Antenna Placement

When the VTX or VRX units are bodyworn the antenna should beplaced as high and as straight as is practical. A transmitteror receiver will typically be worn under the arm and the antennashould be run upward over the shoulder. This helps improve theeffective radiated power of the transmitter and the gain of thereceiver antenna.It should be remembered that any object close to the transmitterwil l invariably reduce i ts power output. In bodywornappl icat ions the effect is qui te considerable. When used infixed installations the antenna should be as straight as ispractical and sited away from objects,Where the transmitter's effective output power has been reduceddue to circumstances beyond control improving the receiver'santenna site can dramaticaly improve performance. (Elevating thereceiver and i ts antenna is general ly effect ive.)The receiving site should be as high as possible and( i f poss ib le) in the l ine o f s igh t w i th the t ransmi t te r. Arigid whip antenna can be used in preference to a flexible type.Direct ional antennas wi l l give excel lent results but aregeneral ly bulky.

6

Section 4

VTX-12 and VTX-22 Transmitters

4.1 In t roduct ion

Paragraphs 4.2 to 4.10 inclusive are also applicable to the VTXSseries transmitters which incorporate the Audiotel miniaturespeech scrambler module.

4.2 Control Switch

The front panel rotary switch has six positions corresponding to'off (0) , 'Bat tery Test ' (T) , and microphone gams 1, 2, 3, and4 (highest) .

In the 'T' battery test posit ion the front panel LED (LightEmitt ing Diode) wi l l i l luminate to indicate the state of the_battery. The LED will begin to dim at around 7V and extinguishat approximately 6V. The transmitters wil l perform withinspecification up to the point at which the LED extinguishes.In posi t ion 'T ' the uni t is t ransmit t ing. In normal useposition 1, 2, 3, or 4 is choosen. The LED will in theseposit ions indicate that the transmitter is act ive and thebat tery s tate.To save power and to maintain unobtrusive operation the LED maybe disabled using the switch under the rear panel, seefigure 1 . The LED w i l l s t i l l i l l umina te a t pos i t i on T .

During VOX (voice activated) operation the LED can be used toset the most suitable gain position. After setting the LED canbe disabled as described above.

4.3 Microphone Gain Position

The four gain positions provide approximately 10dB incrementswith posit ion 4 giving the highest gain. When the transmitteris used in the VOX mode the gain selection also determines thethreshold above which audio signals will activate thet ransmi t te r. A t the h ighes t ga in se t t ing th is th resho ld i s a ti ts lowest al lowing the transmitter to be act ivated by low levelsounds.

Gain positions 1 and 2 would typically be used for body-wornapplications whilst 3 and 4 would be used for room monitoringDepending on conditions and microphone types there will be

Fig 1 INPUT SOCKET

ANTENNA SOCKET

VOX—r-NORMAL

®^

£mrnO p

() DEVIATION- +

Fig 2

OFF ONLED

REMOTE

SIONAL

BIAS

GROUND

■BATTERY

INPUT SOCKET

V T X - 1 2 S i V T X - 2 1

exceptions to this and it is worthwhile experimenting indifferent audio environments to famil iar ise the operator withoptimum gain settings.

4.4 Compressor Action

To improve audio quality and to ensure good capture of differingsound levels within an area VTX transmitters incorporate anaudio compressor (or 'automatic gain control - age'). Theeffect is that when sound levels drop (someone talks in a lowvoice) the gain wi l l increase automat ica l ly. I f sound levelsincrease (someone shouts) the gain is reduced automatically.The compressor action is most noticable at position 4.

A good compressor is essential when sound levels into themicrophone are not fixed wi th in re lat ively narrow l imi ts. Thisis certainly the case when a transmitter is placed in a room andthe occupants may at any time be at the other side of the roomor next to the microphone. The compressor will ensure goodcapture of the room sounds even though they may vary widely ini n t e n s i t y.

4.5 VOX Operation

A slide switch beneath the rear panel (see figure 1) allows theoperator to select whether the unit transmits continuously('normal' operation) or only when sound levels exceed athreshold set by the front panel gain switch (VOX operation),

VOX act ivat ion o f the t ransmi t ter g ives great flex ib i l i ty to theoperator. For body-worn use this minimises battery use andal lows hands-free operat ion. In room monitor ing appl icat ionsthis minimises battery use and, in conjunction with a carrieract ived receiver wi th the abi l i ty to contro l external equipment,ensures recording need only occur when there is audio activityin the room under surveillance.

In the VOX mode the standby power consumption (when the unit isnot t ransmit t ing) is less than 1mA. With a f resh alkal inebattery this gives approximately 450 hours of continuousstandby time.When setting the optimum gain position for VOX operation thefront panel LED can be used to indicate activation of thet ransmi t te r.

In the VOX mode the transmitter can be used as an alarm todetect noises made by an intruder. Coupled with the VRX-bLreceiver and the Receiver Interface external alarms can beact ivated automat ica l ly.

8

4.6 PTT Operation

The front panel input socket (see figure 2) allows connection ofa PTT (Push~to~Talk) switch assembly (available from Audiotel).The transmitters can also be activated by other equipment with aTTL (Transistor-Transistor Logic) compatible switch output.Switching sense is:

Closed circuit for standby

Open circui t for t ransmit

Standby power consumption is less than 1mA for VTX/VRX units andapproximately 10mA for VTXS/VRXS units.The telephone interface described in section 9 operates thetransmitter through the PTT control input.

Magnetically operated reed switches such as those used in doorsensors for intruder alarm systems can be used to activate thet r ansm i t t e r.

4.7 Repeater Operation

Controlling the transmitter via the PTT switch input with areceiver with a compatible squelch output such as the AudiotelVRX-SL or ML and feeding the audio output from the receiver intothe transmitter forms an automatic repeater.

When used in this mode two operating frequencies should beseparated by at least 2 MHz. It is also necessary to space thetransmitter and receiver antennas as far apart as possible(at least 2 metres), see figure 3. This helps reducedesensi t isat ion of the receiver by the t ransmit ter. Leadassemblies for repeater operation are available from Audiotel,

4.8 Remote Control Operation

If the audio input to the transmitter in the repeaterconfiguration described in 4.5 above is provided by a microphonethen the system becomes a remotely control led transmitter. I tshould be noted that the command transmitter must transmitcontinuously in order that the remote transmitter be active.

4.9 Transmitting Times

Approximate continuous transmitting times are as follows forfactory f resh a lka l ine bat ter ies :

9

31£CO

<HX

< >f M

33CD

T3CDDJ»CD

oCD

03

o3

<uX

I

V T X - 1 2 2 0 h o u r sV T X S - 1 2 1 5 ( s t a n d b y t i m e - 4 5 h o u r s )

V T X - 2 2 3V T X S - 2 2 3 ( s t a n d b y t i m e - 4 5 h o u r s )

Allowance has been made for slightly increased currentconsumption when a practical (non-50 ohm) antenna load ispresented to the t ransmit ter 's output ampl ifier.Due to various factors users may find that units givelonger operating times.Units will transmit even when the battery indicator LED hasextinguished. Power output wi l l progressively decrease andaudio performance will degrade.

4.10 Connection of User's Accessories

The multi-pin input socket allows connection of 2 and 3-wireactive microphones together with passive types. PTT switchassemblies, either mechanically switched or electonic areconnected via the same socket. See figure 2 for pindesignations and refer to Appendix A for input sensitivity andimpedances.

Special input assemblies can be made to order, please contactthe Sales department.

4.11 Scrambler Operation - VTXS Series Only

The miniature slide switch on the scrambler housing selectsscrambled or normal operation, see figure 4.

10

F i g 4

@

(

(Si

>

<s

7

—;

NORMAL-WHITE

-SCRAMBL ED

RED

__=_ o(L3)o __-..

P°%Ol^ ®2 1

V T X S - 1 2 S . V T X S - 2 2

Section 5

VRX-SL Receiver

5.1 Int roduct ion

Paragraphs 5.2 to 5.8 inclusive are also applicable to theVRXS-SL receiver which incorporates the Audiotel miniaturespeech scrambler module.

5.2 Control Switch

The front panel rotary switch has six positions corresponding to'off (0), 'Battery Test ' (T), and headphone/earpiece volumesett ing 1, 2, 3, and 4 (h ighest) . See figure 5.In the 'T' battery test posit ion the front panel LED wil li l luminate to indicate the state of the battery. The LED wi l lbegin to dim at around 7V and extingish at approximately 6V.The receiver wil l perform to specification up to the point atwhich the LED extinguishes.

In posit ion 'T' the receiver is act ive and the volume sett ing isapproximately 3. During battery test headphones or earphones asappropriate should be connected. The associated transmittershould also be active to lift the receiver squelch and thusprovide an audio output to the headphones.

5.3 Volume Setting

The four positions provide approximately 8dB increments tosuit individual preferences and to enable a wide range ofearpieces of di ffer ing efficencies to be used with the receiver.Loudpseakers may be connected but they must have an impedance of8 ohms minimum and should be efficient.

5.4 Squelch Sett ing

The squelch threshold (that is, the radio signal level abovewhich the transmitter 's signal at the receiver 's antenna wi l lturn the receiver on and activate the headphone/earphoneamplifier and any external equipment through the squelch output)is adjustable via a small screwdriver adjusted preset beneaththe rear panel, see figure 5. This threshold is factory set at0.3uV. Rotat ing this control ant ic lockwise decreases thisthreshold unt i l the receiver squelch is l i f ted regardless ofwhether the t rasnsmit ter is act ive or not . Rotat ing the contro lclockwise increases the threshold.

11

Fig 5 OUTPUT SOCKET

ANTENNA SOCKET

o

BATTERY

Fig 6

i ) S Q U E L C H- +

RECORDER

HEADPHONES+ VE

HEADPHONES- VE

SQUELCHP REMOTE

OUTPUT SOCKET

V R X - S L

5.5 Output Socket

The front panel mult i-pin socket provides the fol lowing outputs:

Headphone/earphone audioRecorder audio (independent of volume setting)

TTL compatible squelch output

Figure 6 gives the pin designations. Multi-way output leadassemblies are avaiable from Audiotel together with specialassemblies made to customer order. For output levels pleaserefer to Appendix B.

5.6 Control of External Equipment

The squelch output is an electronic switch whose action dependson whether the squelch threshold has been exceeded. If thetransmit ter is act ive and within range the squelch wi l l l i f t .Switching sense of the switch is as follows:

Sque lch l i f t ed - Ou tpu t open c i rcu i tReceiver muted - Output c losed circui t

The squelch ouptut is formed by an open-collector transistor.This output is not suitable for power switching and is intendedfor TTL compatible inputs only. Where heavier loads are to beswitched then the receiver interface unit should be used. Thisis described in Section 8.

Through the squelch output an external piece of equipment suchas a tape recorder will only operate when the transmitter isactive. When used in conjunction with a VOX activatedtransmitter then the recorder only runs when there is audioac t i v i t y w i th in the a rea under su rve i l l ance . I f t hetransmitter is activated by, say, a panic switch or intruderdetector switch, the output can be used to trigger an alarm.

5.7 Repeater & Remote Transmitter Control Applications

Please refer to Section 4, paragraphs 4.7 and 4.8.

5.8 Operating Times

The operating time with a factory fresh alkaline battery dependson the mode and the impedance of the headphones or earpiece.Typical operating times are as follows:

12

N o H e a d p h o n e s , r e c e i v e r m u t e d 3 5 h o u r s

N o H e a d p h o n e s , s q u e l c h l i f t e d 2 5 h o u r s

300 Ohm Headphones, sque lch l i f ted 25 hours

8 O h m L o u d s p e a k e r, s q u e l c h l i f t e d 1 2 h o u r s

5.9 Scrambler Operation - VRXS-SL Only

The miniature slide switch on the scrambler housing selectsscrambled or normal operation, see figure 7.

13

F i g 7

* 0 ^ 7

©

J

NORMAL

WHITE

SCRAMBLED

RED

V R X S - S L

Section 6

Vehicle Power Supply

6.1 Int roduct ion

The vehicle power supply allows a VTX transmitter or VRXreceiver (or both) to be powered from a vehicle 12 or 24 VDCnegative earth supply.On no account should VTX or VRX units be directly connected tovehicle electr ical systems

The power supply provides a regulated output of 7.2 VDC free ofinterference and potentially damaging high voltage spikes.

See figure 8 for input/output sockets and indicator detai ls.

6.2 Input

The vehicle supply is connected via a three-pinself-latching connector. See Appendix C for maximum inputra t ings . The input is e lec t ron ica l ly and fuse pro tec tedagainst sustained overloads and reversed connections.

6.3 Output

The output is via a two-pin self- latching connector. Twosockets are provided but the total power available is 250mA at7.2 VDC. If the output is short-circuited or overloaded then thepower supply will automatically shut down without damage. Toreset disconnect and reconnect vehicle supply after removing theoverload.

Connection to the VTX or VRX unit is made by replacing the rearpanel of the VTX or VRX unit with the panel provided in thepower supply ki t . Cl ip the two battery connectors together,assemble the new panel onto the unit and connect the power leadfrom the power supply.

6 .4 Ind ica tor

The red LED on the front panel indicates that the vehiclesupply is present and that a regulated output is available.

14

6.5 Accessories

The following accessories are suppied with the unit and theseshould be checked on unpacking.

Vehicle Supply Connection Lead

Output Connection Lead

VTX/VRX rear panel with connection socket

Any shortages must be notified at once to Audiotel.

15

Fig 8

OUTPUT SOCKET

LED

INPUT SOCKET

+ VE

+ VE

NO CONNECT!

- V E

OUTPUT SOCKET7-2 VDC

INPUT SOCKET11-30 VDC

V T X - V R X V E H I C L E P S U

Section 7AC Power Supply

7.1 Int roduct ion

The AC power supply allows a VTX transmitter or VRX-SL receiver(or both) to be powered from either a 100/110 or 220/240 VACsupply. Units are preset by Audiotel.Audiotel does not advise the use of simple battery eliminatorsas these wil l cause interference in the audio circuitry withinthe transmit ter or receiver.

The power supply provides a regulated output of 7.2VDC atmaximum current of 250mA which is electronically protectedaga ins t shor t c i rcu i t o r sus ta ined over load . P lease re fe r toAppendix D for fu l l specificat ions.

7.2 Input

The AC input is via a permanent three-wire cable. Whencorrect ly connected this grounds the chassis of the unit . Toavoid the possibi l i ty of injury or death the chassis, via thecable supplied, must be grounded before AC power is supplied.Any extension cable or isolating transformer supply must providea suitable earth connection.

Power cable connections are as follows:

B r o w n = L i v e

B l u e = N e u t r a l

Yellow/Green = Earth or Ground

7.3 Fuses

The input is fuse protected, spares are supplied in theaccessory kit. The fuse rating of 50mA must not be exceeded.

7.4 Output

The regulated output is via a two-pin self-latching connector,Two sockets are provided but the maximum total power outputavai lable is as specified in 7.1 above. Please refer to figure9 for output connector and indicator details.

16

F i g 9

OUTPUT SOCKET

FUSE HOLDER

+ VE

OUTPUT SOCKET7-2 'VDC

V T X - V R X A C P S U

Connection to the VTX or VRX unit is made by replacing the rearpanel of the VTX or VRX unit with the panel provided in thepower supply k i t . Cl ip the two battery conectors together,assemble the new panel onto the unit and connect the power leadfrom the power supply.

7.5 Ind icator

The red LED on the front panel indicates that the AC supply ispresent and that the regulated output is available.

7.6 Accessories

The following accessories are supplied and these should bechecked on unpacking:

Output Lead

Spare Fuse Kit

VTX/VRX rear panel with connection socket

Any shortages must be notified at once to Audiotel.

17

Section 8

Receiver Interface Unit

8.1 In t roduct ion

The receiver interface unit allows a wide range of equipment tobe controlled by the squelch output of the VRX-SL receiver. Atypical appl icat ion is automatic control of an external taperecorder.

The inter face uses the TTL ( t ransistor- t ransistor- logic) outputfrom the receiver to dr ive an internal latching relay. Bothnormally closed and normally open switch actions are available.Please refer to Appendix E for specifications of the relay.

The interface operates from a PP3 Alkaline battery. Powerconsumption is so low that an on-off switch is not necessary.The battery wil last approximately 10 months when not in use andwill provide power for over 1000 switching operations.

8.2 Inputs

The connecting lead provided links the VRX-SL receiver to theinterface unit. Connection of headphones, audio input of atape recorder etc. is made to the socket provided on theinterface unit . Al l accessories compatible with the VRX-SL arecompatible with the interface.

8.3 Outputs

In addition to providing an identical socket to that from theVRX-SL, a three-pin self-latching socket allows connection tothe relay output.

8.4 Front Panel Control

The small push-button switch on the front panel enables theoperator to manually activate external equipment.

18

Fig 10

PAR ALL EL INPUT j OUTPUT

OVER RIDE

RELAY OUTPUT

RECORDER AUDIO

HEADPHONES

GROUND

REMOTE

NORMALLYOPEN

COMMON

NORMALLYCLOSED

INPUT-OUTPUT SOCKET RELAY SOCKET

V R X I N T E R F A C E

8.5 Accessories

The following accessories are supplied and these should bechecked when unpacking:

VRX-SL to interface connecting lead

Relay output leadReceiver outlet lead assembly

PP3 battery

Any shortages should be notified at once.

19

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Section 9VTX Transmitter Telephone Adaptor

9.1 In t roduct ion

The VTX telephone interface unit allows either a VTX-12 orVTX-22 transmitter to be connected to a telephone line forautomatic transmission of the telephone conversation. Thetransmitter is only active when the handset is l i f ted.

9.2 Operation

The telephone interface detects the voltage drop on thetelelphone l ine pair as the handset is l i f ted. Where loopimpulse diall ing sytems are in use the transmitter wil l switchrapidly on and off during the dialling pulse sequence.In the standby mode, that is when the handset is down, thetransmit ter wi l l drain approximately 1mA from i ts battery giv inga total standby time of up to 450 hours. VTXS transmittershave a standby current drain of 10mA giving standby times of 45hours.

Total transmitting time is dependent on the duty cycle of theparticular telephone line and the power supply for thet ransmi t ter. I t i s not poss ib le to power the t ransmi t ter f romthe telephone line.

9.3 Connection to the Telephone Line

Please see figure 11. Connection to the telephone line may bemade anywhere between the telephone handset and the localexchange. A paral lel connection is made. The impedancepresented to the line is high and the current drain at anon-hook voltage of 50 V is less than 60 microamps. Pleaserefer to Appendix F for specifications.

The interface is powered from the telephone line.

9.4 Connection to the Transmitter

Connection is made via the 4-pin self-latching plug. Thetelephone interface uses the PTT input to control thet r ansm i t t e r.

20

Audio gain to suit the l ine conditions is set by the frontpanel control switch of the transmitter. The compressor wil ltend to equal ise audio levels to improve in te l l ig ib i l ty.

9.5 Automatic Recording

When used in conjunction with the VRX-SL receiver and,depending on the type of tape recorder used, the receiverinterface, automatic recording of telephone cal ls isposs ib le .Use of an AC power supply or large capacity battery packstogether with the Audiotel Auto-cascade recorder permits longterm automatic surveillance and recording of the targettelephone.

21

Appendix AVTX & VTXS Specifications

Output Power

Frequency Range

Frequency ToleranceModulation

Deviation

Adjacent ChannelPower

Spurious EmissionsAudio Sensi t iv i ty

Input Impedance

Microphone BiasAudio Bandwidth

Compressor DynamicRange

VOX Operation

VTX 12 20mWVTX 22 200mW

(50 ohm load)(50 ohm load)

Remote Control

Supply VoltagePower source

To be specified within 140 - 175 MHz

+/- 1 kHz, -10 C to +60 CNarrowband FM

+/- 2.5 kHz peak (12.5 kHz channel spacing)+/- 5.0 kHz peak (25.0 kHz channel spacing)Less than 200nW

Any one less than 250nW150uV RMS gives 60% of maximum deviation(1 kHz, at maximum gain)Active Microphones, nominally 10K ohms.Passive Microphones, nominally 50K ohms

4V nominal

3 kHz nominal

50dB variation in input level gives lessthan 6dB variation in peak deviation (atmaximum gain)

Transmitter is switched from standby totransmit by signals greater than -6dBrelative to compression threshold. VOXrelease time 5 seconds.

Provision for external PTT or electronicswitching. Open circuit - on, closedcircuit - standby. Compatible with TTLopen collector devices.6.0 - 10.0 VDC, reduced performance to 5V

Internal PP3 Alkal ine battery. Rear panelswith power input socket available

22

Bat tery L i fe VTX 22 continuous transmit, approx. 3 hoursVTX 12 continuous transmit, approx. 20hours

Output PowerVa r i a t i o n

Supply Current

Less than +/- 1.5dB (into given load) +15to + 35 C for 6.0 to 10.0 VDC.

VTX 12 Standby, less than 1mAVTX 22 Standby, less than 1mA

VTX 12 Transmit, less than 21mAVTX 22 Transmit, less than 110mA

VTXS-12 Standby, less than 11mAVTXS-22 Standby, less than 11mA

VTXS-12 Transmit, less than 31mAVTXS-22 Transmit, less than 160mA

The above are for a 50 ohm loadand disabled front panel LED

Front Panel Control 6 posi t ion rotary switch for off ,battery, test and 4 gain posit ions

Single LED for battery test andtransmit

(Under battery cover). VOX/Normalselect and LED disable

Black Nextel, other colours to specialorder

See diagram

Including battery 245g

Front PanelI nd i ca to r

Rear Controls

F in ish

Size

Weight

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Appendix BVRX-SL & VRXS-SL Specifications

Frequency

Frequency ToleranceModulation

S e n s i t i v i t y

Squelch Threshold

Adjacent ChannelRejection RatioSpurious ResponseRejection RatioIntermodulat ionRejection RatioDesensi t isat ion(Blocking) Level

Spurious outputs

Outputs

Power Supply

Supply Current

Front Panel Control

To be specified within 136 - 175 MHz

+/- 1kHz, -10 deg C to +60 deg CNarrowband FM. 12.5 kHz or 25 kHzchannel spacing to be specified attime of order

-107dBm (luV) signal modulated by 1 KHztone with a peak deviation of 2.5 kHzproduces an output s+n/n ratio greaterthan 26dB

-120dBm (0.2uV) nominal. Adjustablethrough control under battery coverBetter than 75dB

Better than 60dB

Better than 60dB, measured as per MPT 1301

Better than -23dBm

Less than -47dBm (20nW)

Recorder - 50mV RMS (typical) into 20Kohms, independent of volume setting

Headphones - 60mW typical into 8 ohms

Squelch - Open collector/-ve ground. 'On'when receiver is muted

6-10 VDC. Internal PP3 Alkal ine battery

Less than 21mA with squelch lifted and noheadphones.

Sing le 6-pos i t ion swi tch for o ff , bat terytest, and 4 volume settings

24

Fig 13

INPUT SOCKET

+ VE

- VE

INPUT SOCKET7-2 VDC

V T X S . V R X P O W E R P A N E L

Front Panel Indicator Single LED for battery test

R e a r C o n t r o l ( U n d e r b a t t e r y c o v e r ) . S q u e l c h t h r e s h o l d

F i n i s h B l a c k N e x t e l , o t h e r c o l o u r s t o s p e c i a lorder

S i z e S e e d i a g r a m

W e i g h t I n c l u d i n g b a t t e r y 2 4 5 g

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Appendix CVehicle Power Supply Specifications

Input Voltage

Output Voltage

Output Current

Output RippleConnections - Input

Connections - Output

Input Protect ion

Output Protection

OperatingTemperature RangeSize

11 to 30 VDC, negative ground

7.2 VDC +/- 0.2 VDC

Maximum 200mA continuous

Less than 5 mV pk - pk

Lemo 3-pin polarised self- latchingconnector

Lemo 2-pin polarised self- latchingconnector, 2 offFusible Resistor against sustainedover load or in terna l fa i lu re ,passive and active protection againsttransient peak and reverse voltages

Elect ron ic against shor t -c i rcu i t andoverload. Thermal shutdown on overheating

-10 deg. C to +60 deg. C

55x63x23 mm (excluding leads)

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Appendix DAC Power Supply Specifications

Input Voltage

Output Voltage

Output Current

Output RippleConnections - Input

Connections - Output

Input Protect ion

Output Protection

OperatingTemperature RangeSize

110/120 or 220/240 VAC7.2 VDC +/- 0.2 VDC

Maximum 250 mA at 120 or 240 VACTypically 175 mA at 100 or 200 VACLess than 10 mV pk - pk

Hardwired 2 metre 3-core cable

B r o w n - L i v eB l u e - N e u t r a lYellow/Green - Earth or GroundLemo 2-pin polarised self- latchingconnector, 2 off50 mA anti-surge fuse

Elect ron ic against shor t -c i rcu i t andoverload. Thermal shutdown on overheating

-10 deg. C to +60 deg. C

120x63x23 mm (excluding leads)

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Appendix EVRX-SL Receiver Interface Specifications

Input

Outputs

Relay Rating

Power Supply

Battery L i fet ime

Size

Direct from VRX-SL receiver. Relaydrive compatible with TTL externalcontro l , open col lector open c i rcui t for' o n ' , c l o s e d c i r c u i t f o r ' o f fIdentical outputs to VRX-SL receiver viaLemo 4-pin polarised self- latchingconnector

Relay contacts via Lemo 3-pin polarisedse l f - l a t ch ing connec to r. Connec t ionsfor common, normally open and normallyclosed switch actions

Maximum switching power - 35W/60VAMaximum switching volt. - 150 VDC, 125 VACMaximum switching current - 2A (resistive)

Mechanical Life, better than 100,000,000operat ions5.5 - 10 VDC via internal PP3 Alkalineba t te ryBetter than 1000 relay switchingoperations, 10 months on standby98x63x23 mm (excluding leads)

28

Appendix FVTX Telephone Interface Specifications

Connection

Outputs

Output Lead

Input ImpedanceCurrent Drain

Power Requirements

Size

2-wire paral le l to te lephone l ine pair

Audio via isolating transformer app. 5 mVControl v ia sol id state switchopen-circuit when telephone line voltageis less than app. 25 V, closed-circuit(7 ohms) when telephone line voltage isgreater than app. 25 VAudio and control via ready-wired 0.5mlead terminated in a Lemo 4-pinpolar ised sel f - la tch ing connector

DC, greater than 2 MohmAt 50 VDC on-hook voltage current drainfrom telephone line is less than 30 micro-amperes

Self-powered from telephone line30x20x15 mm (excluding leads)

Unit is completely encapsulated and is non-servicable

29

Appendix G

Speech Scrambler Options Specifications

Method

Codes

Inversion Band

Frequency ResponseCarrier Accuracy

Signal Leakage

Upper SidebandReject ionCarr ier Reject ion

Control

Size

Fixed frequency inversion

Single350Hz to 3400Hz

-3dB, better than 450Hz to 3400Hz

Crystal control led, better than 5HzBetter than -40dB at 1kHz, lOdBbelow cl ipping level

Better than 30dB

Better than 45dB referred to clippingl e v e l

Normal/Scramble selectAdds 60x27x6 mm block to top large sideof t ransmit ter or receiver

30

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