TCA-B

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TCA-B

Telephone call analyzer

TCA-B was a portable single-channel telephone call analyzer for analogue subscriber telephone lines, developed around 1979 by Zellweger in Uster (Switzerland). The device was intended for use by telecom operators and for Lawful Interception (LI). It was able to register telephone call data, such as time and duration of a call, and the phone numbers of the calling and called parties.

The device measures 275 x 226 x 135 mm and weights 3730 grams. It was supplied in a brown carrying case with pockets for the accessories. It can be used on its own (stand-alone), or as part of a lawful interception (LI) tapping room setup.

At the front is a DA-15 socket to which the line under surveillance is connected. When a call is initiated (incoming or outgoing), any call traffic information (metadata) that is provided by the telecom operator, will be printed onto the built-in thermal printer. The image on the right shows a typical single-line setup, with break-out box.

The TCA-B was used by many telecom operators in Europe as a stand-alone device for testing and monitoring the performance of telephone lines, dial pulses, DTMF tones, information, cost pulses, etc. It was also used by law enforcement agencies (police) and intelligence services, for gathering forensic evidence in criminal investigations. It can only register metadata and not the call content. The device shown here, was used for many years in one of the analogue tapping rooms of the Dutch police, until they were replaced by digital (later: software-based) products.

HELP REQUIRED — We are still looking for the operator's manual of the TCA-B, in order to get a better understanding of the operation of the device, its features and its applications. Please help us to expand this page by providing additional information. Reports from former users and eyewitnesses are also welcome. ➤ Contact us

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TCA-B with storage case ad break-out box

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Connection diagram (printed at the bottom)

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Instructions printed at the back of the device

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Versions

TCA-A
This model is believed to have been introduced around 1970 for use on exchanges with impulse dialling and limited signalling. The exact details are currently unknown.
TCA-B
This model is believed to have been introduced around 1979. It is programmed by means of a rotary selector (MODE), a set of 8 numeric thumbwheel selectors and an execute button. This is the model that is described on this page.
TCA-C
This model is believed to have been introduced around 1990. The thumbwheels of the TCA-B have been replaced by a numeric LED display and a 16-button telephone keypad, allowing easier input of the initial settings. See this image from Nordlandsmuseet [2].


Features

The diagram below gives a quick overview of the control and connections on the front panel of the TCA-B. The device is connected to the analogue subscriber line (under surveillance) and a 48V DC power supply, via the 15-way DA-15 socket at the bottom right. The controls on the front panel are enabled by setting the key-operated switch at the bottom centre to the ENABLE position. This allows the date, time, operator number, exchange number, etc. to be programmed.

Programming is done by setting the MODE selector at the centre to the desired position, entering the required data on the thumbwheels at the top, and pushing the EXECUTE switch upwards. Once all data has been entered, the key is returned to the LOCK position, so that no data can be altered anymore. The line under surveillance will now be monitored and the LEDs along the right side of the front panel, will show the current status and any alarms. As soon as an incoming or outgoing call is initiated, the metadata will be printed on the thermal printer at the left.

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Lawful interception LI

In most countries, lawful interception (tapping) is restricted by a complex set of laws. For this reason, the TCA-B only registers the metadata and not the call content. For recording the call content, a separate system had to be used.

In the Netherlands, the TCA-B was used in the analogue tapping rooms of the police and the intelligence services. A tyical setup of the 1980s is the ATR shown in the image on the right.

➤ More information

Recorder and printer connected to tapping unit


Operation


External settings

The full operating instructions are printed in the user manual, which is unfortunately missing from the device in our collection. Luckily, they are also printed on the metal back panel of the device, along with instructions on how to replace the thermal paper. A quick summary:

Connect unit to 48V DC power (LED POWER on)
Reset acoustic alarm (press RESET ALARM)
Select EVENTS or SUMMARY
Set key to ENABLE
Set MODE selector to SET DATE
Enter date (e.g. 19790312) and press EXECUTE
Set MODE selector to SET TIME
Enter time (e.g. xx134820) and press EXECUTE
Set MODE selector to SUBSCRIBER NUMBER
Enter subscriber number (e.g. 00416393) and press EXECUTE
Set MODE selector to EXCHANGE NUMBER
Enter the exchange ID number (e.g. 00000055) and press EXECUTE
Set MODE selector to OPERATOR NUMBER
Enter the operator ID number (e.g. 00077021) and press EXECUTE
Set MODE selector to METER/START MEASUREMENT
Enter counter position (e.g. 00763152) and press EXECUTE
Set MODE selector to METER/END MEASUREMENT
Enter counter position (e.g. 00763781) and press EXECUTE


Internal settings

In addition to the external settings described above — which can be entered by the user — there are a number of internal settings, which allow the device to be customised for a specific protocol, country, exchange or application. This requires setting some straps (jumpers), altering removable resistors and ultimately swapping a Programmable Read-Only Memory (PROM) on the board.

The internal settings are located behind a hinged metal panel at the rear side of the device, and requires loosening one screw. The instructions are printed on the inside of the lid as shown here. Behind the panel is also a socket (embedded in the PCB) marked Interface Connector. Although the pupose of this socket it currently unknown, it allowed the system to be expanded later.


Parts


Case	TCA-B	Break-out	Cable	Paper


Storage case

The TCA-B was supplied in a dark brown nylon storage case, like the one shown in the image on the right. The largest compartment takes the device, of which the grip protrudes the lid.

At the front are two pockets for the break-out box, the cables, spare printer rolls, etc.


TCA-B

The TCA-B is a fully autonomous device that can interpret the signalling data from the telecom provider – sent by means of AFSK or DTMF tones before the call is answered – as well as the DTMF tones of a push-button telephone and the pulses of an old dial telephone, and print them onto the thermal printer at the left.

The device is powered by 48V DC – which was a common DC voltage in any analogue telephone exchange – via the break-out box below.


Break-out box

All connections to and from the TCA-B,incuding the external power supply, are via the DA-15/P socket at the bottom right of the front panel. In a stand-alone setup, the break-out box shown in the image on the right, should be connected to this socket, using the supplied 15-way cable.

The breakout box has a 10 banana-sockets, for connection of the external 48V power supply, the line under surveillance and for controlling the motor of a tape recorder. Furthermore, it provides three isolated alarm (relay) contacts.


Cable

All connections to and from the TCA-B, incuding the external power supply, are via the DA-15 socket at the bottom right of the front panel. The 15-way cable shown in the image on the right was supplied with the set and was usualy stowed in the right pocket of the carrying case.

The cable can be used to connect the TCA-B to the break-out box shown above, or to other equipment, such as a police tapping room setup.


Thermal paper

The TCA-B has a built-in thermal printer that can not be used with regular paper from, say, a calculator or a cash register. Instead it needs thermochromic paper, that changes colour when it is heated by the print head [3].

Although this was a standard type and size of printing paper at the time the TCA-B was sold, it is far less common today. Some types of thermal paper were even abandonned under pressure of environmental activists, because of unconfirmed health issues [3].

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Interior

The device is made of high quality passivated steel, sprayed in two colours: orange and brown, with a fine eye for detail and precision. The interior can be accessed by removing 6 screws along the edges of the rear panel: two at the orange top and two at each of the brown side panels.

After removing the six screws, the hinged rear panel can be lowered, revealing a large board (mounted to the rear panel), a data-entry board (fitted to the front panel) and a printer control board (fitted to the rear of the printer).

The image on the right shows the board, which consists of an internal switched-mode power supply unit, a 8085 microprocessor with EEPROMs and RAM, and interfacing circuitry. The boards are designed by Zellweger AG — ZAG — around 1979 and – judging from the date codes on the components – were built around 1989.

Close to the upper edge of the CPU board is a small daughter card with the DTMF receiver. It is not made by Zellweger, but was provided as plug-in solution by Dutch ICT security company Group 2000, who was also the supplier of a number of tapping rooms of the Dutch police. The board holds a single hybrid circuit on a ceramic substrate - in the shape of a 40-pin Integrated Circuit (IC) - with a complete DTMF decoder, made in 1984 by Teltone Corporation (USA) [a].