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Telestar 12x
Message terminal

Telestar 120, 121 and 122, were text terminals, or correspondence devices, 1 introduced in June 1976 by AEG Telefunken in Frankfurt (Germany). The device was intended for data transmissions (text) via standard voice communications channels such as analogue telephone lines and HF radio links. The device was used by the German Police (INPOL), the BGS 2 and to some extent by NATO. Telestar supports data rates between 50 and 9600 baud, and is teleprinter (telex) compatible. 3

The Telestar terminal is housed in a compact strong aluminium die-cast enclosure, with a hinged sub-section that contains the thermal printer. When closed, the device is no bigger than a standard typewriter. When opened, the printer is tilted upwards, revealing keyboard and controls, as shown in the image on the right.

An ergonomic full-size keyboard is used for the input, whilst the output is printed directly to the thermal printer that uses a special kind of A4-wide metalized paper, similar to the paper used on old weather fax receivers like the NAGRAFAX.
Telefunken Telestar 121

The name TELESTAR is an acronym for Telefunken Symbol Transmitter And Receiver. Apparently, public services were not concerned about privacy at the time. Although the device was advertised by Telefunken as suitable for secure transmission [A], the data was not encrypted. In this context, the word secure was related to data integrety rather than privacy. The only 'security measure' that was taken, was the use of ODD PARITY checking and the use of 2 stop bits in the asynchronous serial data protocol. Encryption was optionally available by adding an external TELEKRYPT unit.

Telestar 121 terminals were used by the German Police for online checking of car registrations, ID checks, criminal records, terrorist activity, human trafficking, drugs, weapons, etc. via their INPOL information system. They were commonly installed inside a police vehicle and were connected to the existing FuG-7b, FuG-8b or FuG-9b VHF/UHF FM radio. As no data encryption was used, this was definitely a breach of privacy by today's standards. It should not come as a surprised that much of the data was intercepted and logged by the East German security service, the Stasi [3].

  1. In press releases, Telefunken referred to the device as Korrespondenzgerät (correspondence device).
  2. BGS = Bundesgrenzschutz (Border Police).  More
  3. Teleprinter (telex) compatibility requires the optional 5-level TTY interface to be installed.

Telestar in storage position Unlocking the printer Telefunken Telestar 121 Front view (open) Rear view Power socket Grip AC power cable (100-240V)
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Telestar in storage position
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Unlocking the printer
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Telefunken Telestar 121
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Front view (open)
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Rear view
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Power socket
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AC power cable (100-240V)

All controls of the Telestar terminal are located at the front. When the device is not in use, they are covered by the thermal printer that can be tilted forward, acting as a lid over the keyboard. The diagram below shows the machine ready for use, with the printer/lid on top of the terminal.

Overview of controls of the Telestar 121

The machine can be powered by the AC mains (100-240V) or by an external DC power source (10-32V) such as the battery of a car. Both can be connected to the 7-pin Hirschmann socket at the rear. Suitable cables were usually supplied with the kit. The Telestar has a regular full-size keyboard with either a German (QWERTZ) or an international layout (QWERTY). To the left and right of the keyboard are additional keys that are used to access special features and commands.

All connections are at a recessed section of the rear panel. At the left is the power socket, along with the AC and DC fuses (marked F1 and F2 respectively). Above the power socket are the interface sockets, marked V.24/TTY, FSK and BUS. All interfaces are optional as specified below.

Front view (open) Rear view Connections at the rear Power socket Thermal paper and print head Opening the printer lid Thermal paper supply Printer paper compartment opened
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Front view (open)
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Rear view
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Connections at the rear
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Power socket
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Thermal paper and print head
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Opening the printer lid
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Thermal paper supply
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Printer paper compartment opened

Telestar was available in three versions, each of which has different features. Connection to the outside world was made via a V.24 or a TTY interface. Depending on the version and the required options, the price of a single Telestar unit in 1976 was between DM 12,000 and DM 15,000. 1

  • Telestar 120
    This is the basic model of the Telefunken Telestar that is suitable for on-line use only. Maximum character processing speed 200 bps (bits per second, or baud).

  • Telestar 121
    Similar to the Telestar 120, but with separate transmit and receive buffer for 2000 (optionally 4000) characters each. Transmission of messages is under control of the internal microprocessor. This is the most common Telestar model.

  • Telestar 122
    Enhanced version that is suitable for online and offline use. The send and receive buffers are increased to 4000 (optionally 8000) characters each, and the maximum data transfer speed is 9600 baud. Transmission of messages is under control of the microprocessor.
  1. DM 15,000 ≈ EUR 7,500.

The terminal can be issued with three different interfaces, all of which are optional. For communication with the outside world, at least one interface is needed. The Telestar has two communication channels that can be used simultaneously, identified as Channel 1 and Channel 2.

  • V.24/TTY
    This is an enhanced RS-232 interface that follows the regular V.24 conventions [4]. It can be configured for V.24 use (voltage controlled data signals) or for TTY teleprinter use. In the latter case, current loops are used for sending and receiving data. Note that it can be used as either V.24 or TTY, but not both. The required interface is selected with jumper straps on the interface board. This interface is fitted in most Telestar units.

  • FSK
    For situations were the Telestar has to be used over radio, an FSK interface can be fitted. It has a 15-pin sub-D socket that carries the transformer-coupled audio input and output signals, allowing it te be connected directly to the radio. In addition there are independent relay contacts for controlling the radio's push-to-talk (PTT) function, and switch between microphone and terminal. This interface is fitted in many Telestar units.

  • BUS
    This is a 5-pin sub-D socket that carries direct signals to and from the microprocessor, bypassing the normal command-controlled system. It allows the terminal to be used for a variety of applications. In most Telestar unit, this (optional) interface is not fitted.
  • Grey
  • Yellow
  • Olive green
Security   Telekrypt
Although the data format of the Telecrypt devices provides some level of error correction — it uses ODD PARITY checking — the data sent through its V.24 or TTY interfaces is by no means secure or encrypted. In a military environment, Telestar units were often used via shortwave (SW) radio, by connecting it to a 20W AEG Telefunken SE-6861 manpack radio or a 100W SE-6863 [A].

For secure communication, the Telestar 121 was commonly connected to a Telefunken TELEKRYPT DAT-812 encryptor, as part of the FFT-6856 installation shown on the right. This equipment suite was housed in a military transport case, suitable for mounting in a Jeep, consisting of [B]:
  • Telestar 121
  • Data encryptor TELEKRYPT-DAT 812
  • Forward error corrector FEC-100
  • Driver unit STEU-6856

When transmitting messages via a short wave radio channel, the data transfer rate was limited to 200 baud (in practice typically 50 baud), whilst A7J (A3J) or F1 modulation was used.

The image on the right shows a complete FFT-6856 system in operation. The Telestar unit is installed on a telescopic rail at the bottom of the transport case. At the left – barely visible – is the SE-6861 transceiver with its 100W amplifier.

Note that the German Police did not use any kind of encryption for online interrogation of their INPOL information system at the time, making it very easy for the East German intelligence services to intercept and record the data. More about this below, in the section Compromise.

 More about the SE-6861 and SE-6863

Known use
The following use of Telestar devices has been confirmed:

  1. Used for radio data network between the cities in Rheinland-Pfalz and the regional authorities in Mainz. Possibly also used in other parts of Germany.  Wikipedia

Compromise   Raster IP
During the Cold War, the East German (DDR) intelligence service Ministerium für Staatssicherheit (MfS), or Stasi, was aware of the fact that the German Police used the Telestar for interrogation of its INPOL information system. Stasi Department III subsequently proposed to develop a system that would be able to decode the data signals used for INPOL, decode the information that was sent through INPOL, and store the data for later processing. The system would be called RASTER IP, and it was anticipated that it would take three engineers to develop it in nine months time [3].

A total of 23 RASTER IP systems was eventually built; 18 for use in Linie III, and 5 for use by HV A/VIII. The first research results of RASTER IP were reported on 25 July 1984. At that point, the system had been running for 24 hours a day for 3 months, providing the Stasi intelligence about:

  • Monitoring of travel activity
  • Location of people
  • Confiscated objects
  • Travel documents
  • Police surveillance
  • Drugs
  • Weapons
  • Forged money
  • Ownership
  • Criminal networks
  • Terrorist networks
  • International smuggling
  • Dangerous intensive offenders
  • International criminals
  • Customs supervision
In January of 1987, the Stasi had become aware of the upcoming NATO exercise Wintex/Cimex later that year, and had information that the Telefunken Telestar would be used for the exchange of information between NATO and the German Police. Stasi Department III/12 subsequently put in a proposal for the development of an automated computer-controlled intercept station, that would be able to catch all data in real-time and store it for processing at a later moment [3].
The Telestar 121 terminal has an internal microprocessor with suitable software for entering, storing, correcting, deleting, sending and receiving messages. The system is controlled by means of commands that are entered via the keyboard. Each command is started with the COM-button, followed by a single letter (the actual command) and one or more comma-separated parameters. It is terminated with the ↵ (ENTER) or EOF key.

 Operating instructions

The following red LEDs are present on the indicator panel:

  • Data Set Ready
    Ready for receiving a message
  • Keyboard
    Incomplete message or command entry
  • Transmit channel 1
    Transmitting on channel 1
  • Receive channel 1
    Receiving on channel 1
  • Transmit channel 2
    Transmitting on channel 2
  • Receive channel 2
    Receiving on channel 2
  • Write
    Paper puncher active (option)
  • Read
    Paper reader active (option)
AC mains power cable
DC battery power cable
Spare printer head
Mains power cable
The Telestar has a built-in switched-mode power supply unit (SMPS) that accepts AC voltages in the range 100 - 240V. The cable shown in the image on the right is used to connect the terminal to the mains wall socket.

The three lower pins of the power socket are used for this purpose. Please refer to the pinout section below for full details about this socket.

 Pinout of the power socket
AC power cable (100-240V)

Battery power cable
The Telestar also has a built-in switched-mode power supply unit (SMPS) that allows the unit to be powered by a DC voltage, such as the battery of a car, in the range 10 - 32V. The cable shown in the image on the right is used for this.

The upper two pins of the power socket are used for this purpose. Please refer to the pinout section below for full details about this socket.

 Pinout of the power socket
DC power cable (10-32V)

Spare printer head
The output produced by the Telestar terminal is printed directly onto an A4-wide thermal paper sheet, in a 7 x 5 pixel matrix, much like an ordinary dot-matrix impact printer.

Under normal circumstances, this is completely maintenance-free, as a thermal printer does not require a supply of ink or toner. In the rare event that the print head gets worn-out, it could be replaced by a spare one that was supplied in a small plastic cassette, as shown on the right.
Spare print head in protective packaging

AC power cable (100-240V) DC power cable (10-32V) Power plug Power plug Spare print head Spare print head in protective packaging Spare print head Spare print head
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AC power cable (100-240V)
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DC power cable (10-32V)
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Power plug
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Power plug
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Spare print head
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Spare print head in protective packaging
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Spare print head
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Spare print head

The Telefunken Telestar is extremely well built and is mechanically very strong. The machine is housed in a heavy die-cast aluminium enclosure that holds all circuit boards, the power supply unit (PSU) and the printer. The interior can be accessed by removing 8 screws from the bottom.

After removing the bottom panel, the large board with the Central Processing Unit (CPU) becomes visible. It holds the 8080 processor, along with RAM memory and the EPROMs that contain the firmware. The CPU is connected to the rest of the machine via ribbon cables.

The CPU board occupies about half the available space. The rear half is taken by the power supply unit (PSU) and the backplane that holds the plug-in interface boards at the other side. The top side of the machine can be removed by removing two screws and loosening a third one.
Interior (bottom view)

This allows the upper case shell (which also holds the printer) to be removed entirely. Note that the bolt at the center is used for locking the blue connector that connects the printer to the CPU. When removing the upper case shell, some pressure may be needed to release the connector.

The remaining lower half is the frame to which all other parts are mounted. Once the upper case shell is removed, the upper side of the interior is exposed as shown in the image on the right. The front half is taken by the full-size keyboard, which is physically located above the CPU board.

At the rear right is the power supply unit (PSU) that consists of three PCBs, housed inside a metal enclosure. The filtered outputs from the PSU are available at the front right. The mains voltage and the battery voltage are both routed via the slide switch at the front right corner.
Interior - top side

At the left are the various interface boards which are installed into the sockets of a backplane, mounted at the bottom of the frame. These boards contains the drivers for the printer as well as the V.24, TTY and FSK interfaces and are responsible for connecting the unit to the outside world.

Interior (bottom view) Backplane holding the interface boards Central Processing Unit (CPU) Loosening the connector Case shell with printer removed Interior - top side Interface boards Power supply unit (PSU)
Connector between printer and CPU CPU board RAM EPROMS and 8080 processor Power supply wiring PSU boards Relay DIP switches
PSU board (1) PSU board (2) Interface board (1) printer control Interface board (2) Interface board (3) Interface board (5) Interface board (6) Interface board (6) - detail
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Interior (bottom view)
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Backplane holding the interface boards
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Central Processing Unit (CPU)
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Loosening the connector
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Case shell with printer removed
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Interior - top side
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Interface boards
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Power supply unit (PSU)
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Connector between printer and CPU
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CPU board
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EPROMS and 8080 processor
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Power supply wiring
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PSU boards
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16 / 24
DIP switches
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PSU board (1)
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PSU board (2)
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Interface board (1) printer control
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Interface board (2)
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Interface board (3)
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Interface board (5)
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Interface board (6)
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Interface board (6) - detail

Although the Telestar is extremely well-built from first-class components, chances are high that after 35+ years of storage, the device no longer works. In most cases this is caused by the fact that tantalium capacitors are used in the PSU and on all boards, for stabilising the power lines.

When switching the device ON after so many years of storage, it will show some activity for one or two seconds and then die. The power LED (to the left of the power switch) will then be OFF again. If this is the case, turn the device OFF immediately in order to prevent further damage.

Inside the Telestar is a selection of orange, red and black tantalium capacitors that may have have deteriorated. The image on the right shows four such capacitors on one of the PSU boards. Replacing just a faulty one will generally not be enough, as the others are also likely to be bad.
Tantalium capacitors on one of the PSU boards

If only the faulty capacitors are replaced, you will probably notice that, after switching the device ON, it will work for a few seconds, until the next tantalium capacitor shorts out. It is strongly advised to replace all caparactors that are connected to the various (+) and (-) power rails.

If you do so, replace them by fresh new (not new-old-stock) tantalium capacitors, or by low-ESR ones, such as Panasonic OS-CON. The image on the right shows the PSU board after replacing the capacitors. Do the same for the CPU board and for all of the interface boards, re-assemble the machine and then turn it ON again. If all goes well, the power LED should now stay ON.

When replacing the capacitors, ensure that they are not too high and that they are mounted close to the board. As some of the boards are fitted closely together, space between them is limited.
Replaced capacitors

It is likely that the above refurbishment is all that is necessary to give the Telestar a new lease of life. If the machine has seen a lot of action though, it may also be necessary to replace the print head, which can be troublesome. Replacement heads were available from Telefunken at the time.

Tantalium capacitors on one of the PSU boards Replaced capacitors
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Tantalium capacitors on one of the PSU boards
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Replaced capacitors

All connections of the Telestar are at the rear panel. It has a rather awkward socket for connection of the mains (AC) or battery (DC) power supply, made by Hirschmann. Furthermore there are sockets for V.24/TTY and FSK equipment. The diagrams below show the pinout of the sockets, when looking at the rear side of the device, straight into the sockets.

Power socket
  1. 100-240V AC
  2. 100-240V AC
  3. not connected
  4. (+) 10-32V DC
  5. (-) 10-32V DC
  6. not connected
V.24/TTY interface
This is a 25-pin sub-D female socket and can be configured internally for either V.24 operation or TTY (line current) operation. Note that the layout for each of these standards is different and that the unused contacts (-) should not be connected.

V.24 interface
  1. GND
    Ground (screen, chassis)
  2. TX
    Transmit data
  3. RX
    Receive data
  4. RTS
    Request to Send
  5. CTS
    Clear to Send
  6. DSR
    Data Set Ready
  7. GND
    Signal ground
  8. DCD
    Data Carrier Detect (signal strength)
  9. -
  10. -
  11. -
  12. -
  13. -
  14. -
  15. TXC
    Transmit Clock (rising edge)
  16. -
  17. RXC
    Receive Clock (falling edge)
  18. -
  19. CTL
    Control channel TX on
  20. DTR
    Data Terminal Ready
  21. -
  22. RI
    Ring Indicate (incoming call)
  23. HS
    High speed
  24. TXC-
    Transmit Clock (falling edge)
  25. -
TTY interface
  1. -
  2. -
  3. -
  4. RTS
    Request to Send (input)
  5. CTS
    Clear to Send (output)
  6. -
  7. GND
    Ground (0V)
  8. -
  9. -
  10. TXA
    Line current TX (+)
  11. TXB
    Line current TX (-)
  12. RXA
    Line current RX (+)
  13. RXB
    Line current RX (-)
  14. RRA
    Line current RX Request (+) [option]
  15. -
  16. RRB
    Line current RX Request (-) [option]
  17. -
  18. -
  19. -
  20. -
  21. -
  22. -
  23. -
  24. -
  25. -
This is a 15-pin sub-D male socket that holds all signals to and from the radio. It also controls the PTT and microphone lines of the radio. Check out the diagram for connection to the FuG-8b to see how the audio lines are interfaced by means of transformers.

  1. FSK in A
  2. FSK out A
  3. Mic switch 1 n.c.
  4. PTT
  5. not connected
  6. FSK out B
  7. not connected
  8. not connected
  9. FSK in B
  10. Mic switch 1 common
  11. Mic switch 1 n.o.
  12. PTT
  13. Mic switch 2 n.c.
  14. Mic switch 2 common
  1. n.o. = normally opened
  2. n.c. = normally closed

Connection to FuG-8b
The diagram below shows how the Telestar terminal was connected to a German FuG-7b, FuG-8b or FuG-9b VHF/UHF FM radio. In this diagram, the terminal is linked directly to the radio, via the FSK interface, without the addition of an encryption device such as the TELEKRYPT.

Options and supplies
Technical specifications
Data standard   CCITT Code Nr. 5 (7-bit ASCII) or CCITT Code Nr. 2 (5-bit Baudot) 1
Data format   1 start bit, 7 data bits, 1 parity bit, 2 stop bits (11 bits, 7O2)
Data speed   50, 200, 600, 1200, 2400, 4800 bps (simplex: 9600 bps)
Printer paper   Metallized paper, 210 mm wide (A4), 23 metres long
Printer speed   75 cps (characters per second) - effectively 35 cps
Printer resolution   5 x 7 dot matrix (thermal)
TX buffer   2000 characters (optional 4000) 2
RX buffer   2000 characters (optional 4000) 2
Main voltage   100 - 240V AC (automatic)
Battery voltage   10 - 32V DC (automatic)
Power consumption   20-28W (DC), 28-37W (AC)
Dimensions (w×d×h)   273 × 291 × 98 mm (147 mm when opened)
Temperature   Storage: -40° to +70° C
Operational: 0° to +55° C (optional: -10°C)
Weight   7.5 kg
  1. Option: Either ASCII or Baudot. User-specific standards available on request.
  2. Telestar 121 and 122 only.

FSK   Frequency Shift Keying
System whereby two different audio tones are used to transmit the digital levels 0 and 1 of a digital data stream. Also known as Audio Frequency Shift Keying (AFSK).
INPOL   Informationssystem Polizei
Nation-wide information system, used by the German Police and the Federal Criminal Investigation Units, for storing and interrogating sensitive information about criminals, criminal offences, terrorist activities, personal data, human trafficking, smuggling, drugs, etc. The system entered service in November 1972 and was improved and extended in the following years.
Stasi codeword for an automated system that was developed to intercept, store and process data from the West-German INPOL information system, that was acquired via radio interception. The codeword RASTER IP was also used for the intelligence derived from the intercepts.
TELESTAR   TELEfunken Symbol Transmitter And Receiver
Crypto Museum are currently looking for the original service manual and the circuit diagrams of the Telestar 121. If you have any information about this device, that is not available in the Documents section below, please contact us.

  1. Brochure, Funkschreib-Einrichtung FFT-6856 / SE-6863
    Feldfunkgerät SE 6861 Datenblatt. Funkschreib-Terminal FFT 6856.
    N 116.106.0. AEG Telefunken. Ulm (Germany).

  2. Telestar 121 Datenblatt
    AEG Telefunken, Ulm (Germany). Datasheet (German).
    N 147.102.2. Date unknown but probably 1980. 8 pages.

  3. Telestar 121 Bedienungsanleitung Kurzfassung
    AEG Telefunken, Ulm (Germany). Short operating instructions (German).
    5X.0172.403.36. March 1981. 18 pages.

  4. Telestar 121 Technische Beschreibung
    AEG Telefunken, Ulm (Germany). Technical description (German).
    Nr. 14/1222. July 1980. 60 pages.
  1. Klaus Paffenholz, Telefunken Telestar 121 - THANKS !
    Received July 2017.

  2. Pionier, Telestar - neue Korrespondenzgeräte von AEG-Telefunken
    Pionier (magazine), Volume 50, Issue 1, January 1977. Page 8-9.
    Retrieved July 2017 via HamFu (Switzerland).

  3. Jörg Drobick, Informationsgewinnung ... Telestar
    SAS und Chiffrierdienst (website). Retrieved July 2017.

  4. Wikipedia, RS-232
    Retrieved July 2017.

  5. Wikipedia (Germany), Katastrophenschutz
    Retrieved AUgust 2017.
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Crypto Museum. Created: Thursday 20 July 2017. Last changed: Sunday, 30 December 2018 - 10:02 CET.
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