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Telsy TX-1020C
Narrow-band radio voice encryptor

The TX-1020C and the TX-1020C Mk. III were voice encryption devices for narrow-band FM radio links, developed by Telsy in Turin (Italy) in the late 1980s. The devices were used most commonly in combination with simplex radios, such as the ones used by the police.
 
Many different versions of the TX-1020C exist. In fact, there was a variant for a wide variety of mobile radio brands and models. As each model may have different audio levels, impedances and channel characteristics, the circuitry of the TX-1020 had to be tailored for that. The unit was usually connected instead of the mike/speaker.

The image on the right shows a version that was made especially for ASCOM radios used with the Dutch Police, as indicated by the designator at the back. This unit was built inside another case (see below), together with a small amplifier PCB.
  
Telsy TX-1020C

When used unmodified, the TX-1020C was connected to the radio instead of the normal microphone (or handset). The TX-1020 effectively took over the function of the microphone and had a Push-To-Talk switch (PTT) at the left. On top of the unit are two buttons, marked 1 and 2, for selection of the appropriate (pre-defined) cryptographic key. To the right of these buttons is a socket for the connection of an external key-filler.

When used outside Italy, encryption devices like the TX-1020C required an export licence during the 1980s and 90s. For most devices this would usually take one month, but in case of the TX-1020C Mk. III it could take up to 90 days [2]. Around the same time as Telsy developed the TX-1020, Philips Usfa (Netherlands) developed a device that showed great similarity. It was called ORTHROS, and was also intended as an add-on for existing radios, but was never released.
 
Telsy TX-1020C Telsy TX-1020C Type plate showing that this is the ASCOM-variant Close-up of the keyboard Close-up of the display Operating the push-button at the side Selecting a pre-set key Fill connector

 
Customization
The TX-1020C and the later TX-2020C could be used in combination with a wide variety of mobile radios, such as Motorola, Philips, BBC and ASCOM. Is some cases, the TX-1020 could be used without modification, simply by using the appropriate cable, but in some cases an additonal modification inside the radio was required. The latter mainly involved power and squelch wiring.
 
The image on the right shows a Telsy TX-1020C built inside a custom case, together with some additional electronics. The top lid of the case contains a number of spring-loaded buttons that indirectly operated the buttons on the Telsy device below them. The SPEAKER-button was omitted. The LCD display was visible through a window in the case, just above the buttons.

An additional PCB is mounted inside the case to the left of the Telsy TX-1020C. It is marked ASC9126A1 COMP., indicating that it was probably developed by ASCOM in June 1991.
  
Telsy TX-1020C mounted inside a custom case (ASCOM)

The short cable from the TX-1020 is connected at various places on the board, and the board is connected to the outside by means of a male DB15 connector at the front left. A metal frame on top of the outer case was probably used as a mounting bracket inside a (police) car.
 
Telsy TX-1020C built inside a custom case Telsy TX-1020C mounted inside a custom case (ASCOM) Close-up of the ASCOM case Connector on the ASCOM case

 
Interior
The TX-1020C is easily opened by removing 6 bolts at the rear. The rear panel comes off and the interior becomes visible. The interior consists of two PCBs: the main PCB that contains all electronic circuits, and a small daughter card that acts as the cable assembly.
 
The cable assembly is held in place by 4 screws and is connected to the main PCB by means of a so-called zebra-connector. The image on the right shows the cable assembly separated from the main PCB. The gold-plated zebra-connector is visible at the center of the main PCB.

The TX-1020C is built around a TMS-320 DSP controller by Texas Instruments, the same one as used in the earlier TX-900, albeit in a square package. It is partly covered by an orange flex-PCB. The TMS-320 is driven by a 20MHz crystal. More detailed images below. Click to enlarge.
  
Cable assembly removed

The small daugther card that was used as the cable assembly, was designed in such a way that it could easily be modified for a particular radio. Many different versions of this PCB existed, complete with a matching cable (see below). The one shown here has an extra two wires that are connected to the orange flex PCB inside the unit.
 
TX-1020C interior Cable assembly separated from the unit Cable assembly removed TX-1020C interior (cable assembly removed) TMS320 DSP by Texas Intruments 10 MHz crystal Connector for cable assembly Unknown microcontroller

 
Compatibility
As stated before, the TX-1020C MkIII was usually supplied to the customer ready for connection to a specific radio. In such cases the appropriate cable assembly was already installed in the unit. The list below shows which radios were supported. The radios that needed a small modification, are marked with a tick in the column 'Modify'.
 
Manufacturer Radio model Telsy cable assembly Modify HF INT800
Alcatel 9220HT 425TX-202-N321 - - -
Ascom SE140 425TX-202-N201 - - -
Autophon SE20 425TX-202-N061 - - -
Autophon SE120 425TX-202-N021 - - -
Autophon SE156 425TX-202-N041 - -
BBC Veriport 1400 425TX-202-N181 - -
BBC Veriport 1900 425TX-202-N031 - - -
BBC Veriphon RT61 425TX-202-N021 - -
Elmer RH4/178 425TX-202-N281 -
Elmer RT-633 425TX-202-N421 - - -
GE PE 425TX-202-N221 - -
Harris RF230 425TX-202-N071 -
ICOM IC-U200T 425TX-202-N301 - -
Italtel MB70 425TX-202-N101 - -
Italtel MB70-D5 425TX-202-N331 - - -
Italtel MB70-D5 425TX-202-N121 - -
Johnson FM5852 425TX-202-N241 - -
Johnson 7151 425TX-202-N251 - -
Kenwood TS50 425TX-202-N451 -
Midland 70-440 425TX-202-N041 - -
Motorola MX300 425TX-202-N171 - -
Motorola MX1000 425TX-202-N231 - - -
Motorola MX2000 425TX-202-N194 - - -
Motorola Radius P210 425TX-202-N351 - -
Motorola MC-MICRO 425TX-202-N291 - - -
Motorola MC-MICRO 425TX-202-N061 - -
Motorola Radius GM300 425TX-202-N131 - -
Nokia RC58 425TX-202-N271 - - -
OTE HP 9000 425TX-202-N401 - -
OTE P80-C 425TX-202-N161 - - -
OTE RMT 246 425TX-202-N411 - - -
Otema S-80 425TX-202-N141 - -
Philips FM1000 425TX-202-N151 - - -
Philips PFX 425TX-202-N011 - -
Prodel V5/32 425TX-202-N081 - - -
Prodel P7/32 425TX-202-N091 - - -
Radiosystem PR460 425TX-202-N341 - -
Siemens ER95A/1 (RV3) 425TX-202-N101 - -
Siemens RV3 425TX-202-N111 - -
Storno CB911 425TX-202-N211 - - -
Storno Stornophone 6000 425TX-202-N091 -
Tadiran RT7330S 425TX-202-N361 - -
Transworld RT100/MP 425TX-202-N391 - -
Teletron FUG 8B-1 425TX-202-N051 - - -
Telettra RH6 425TX-202-N311 - -
Thomson ATR410 425TX-202-N121 - - -
Thomson ATR427 425TX-202-N011 - -
Thomson ATR430 425TX-202-N261 - - -
Thomson ER75 425TX-202-N031 - - -
Thomson TMF213 425TX-202-N111 - -
Thomson TMF300 425TX-202-N441 - -

A tick in the column 'HF' indicates that the HF-circuit of the radio needed to be modified. The rightmost column, marked 'INT800' indicates that the radios are interfaced via a small mobile box adapter that contained an amplifier for an external speaker, together with some interfacing.

In addition to the above pre-assembled cables for specific radio sets, a connector-less universal cable was available for those customers that had sufficient technical background to interface the TX-1020C to their radio. The cable is wired as follows:
 
Colour Name Function Remark
Outer shield SHLD1 Shield Case (housing)
Black GND Power (-) Also PTT ground
Red +VDC Power (+) 6.5 - 30 Volt
Inner shield GND Ground -
Blue PTTP PTT positive +VDC in TX
Mauve PTTN PTT negative GND in TX
White MIKE1 Mic out 600 ohm balanced and insulated, 4Vpp
Yellow MIKE2 Mic out Return
Brown RXIN1 RM input 600 ohm balanced and insulated, 1Vpp
Green RXIN2 RX input Return
Grey SQLCH Squelch input for VHF, UHF (GND to lock)

 
References
  1. Barry Wels
    Donator of the Telsy TX-1020C Mk. III featured on this page.

  2. Telsy S.p.A., Overview of radio sets supported by TX-1020C
    Correspondence between Telsy and unknown party. Date unknown.

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