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Telex
Teleprinter machines - under construction

This part of the Crypto Museum website is dedicated to automatic (digital) telegraphy by means of large typewrite-style devices using a binary code, such as the well-known 5-bit Baudot code, or the 7/8-bit ASCII. Such systems are often called Teletype machines (after the Teletype brand), Teleprinters, Telex (short for Teleprinter Exchange), Teletypewriter or, abbreviated: TTY.

On this website, we will use the generic name Telex to identify the above systems. Teleprinter machines could be operated via land lines (TTY) or via radio (RTTY), mainly using the standard speed of 45.45 baud (USA) or 50 baud (Europe). Punched paper tape was used for storing and (re)transmitting messages. Although telex has been superceeded by modern computers, some computer terminal sessions are still called TTY, for example on UNIX-like systems.

Although Telex machines are not cryptographic devices, many of them were used in combination with external cipher machines and some even had built-in cryptographic capabilities. For that reason, some telex machines are described on this website. For a more exhaustive overview of telex machines, please check out the Telex Museum of Henning Treumann in Germany [1].

Telex equipment that is described on this website:
 
Gretag ETK-47 teleprinter with 14-bit technology ETK-47 Siemens T-68D telex machine T-68D TeKaDe FS-200Z military electronic teleprinter (telex) FS-220 Santec (Helioprint) GNT-4606 paper-tape puncher/reader for telex and computer GNT-4606 Paper-tape repair kit Repair kit

 
Standards
For many years, Telex was the de-facto standard for communication with the Armies world-wide. It was introduced longe before WWII (in 1849) and lasted until the 1990s. It was also used by press agencies, governments, large corporations and by the police. Telex can be employed reliably over (fixed) land lines as well as over radio (HF). In the past, most countries had their own Telex network, consisting of decicated land lines and special exchanges, but towards the 2000s most of them were gradually phased out. Today, Telex is still used by radio amateurs (Hams).

Although most telex systems use the 5-bit digital ITA2 code, generally known the Baudot code, there are systems that use a less-common standards, such as the multi-tone COQUELET code, often used in France, and the 14-bit ETK standard that was introduced by Gretag in the 1950s. Such systems were considered more fault-tolerant but never met wide-spread acceptance.
 
TelexPhone
In order to keep old Teleprinters running and to be able to demonstrate the surviving machines, a group of enthusiasts has setup the so-called TelexPhone project [2]. It allows telex machines to be connected to a hobbyist telex network using standard (analogue) telephone lines (POTS).


A customized modem (TxP) has been developed to convert the special Telex signals into standard modem data, allowing any standard telex machine to be connected to another telex anywhere in the world, without any modifications to the equipment at either side. In the future it will be possible to use the internet as well. A suitable interface (I-Telex) is currently under development.
 
Manufacturers
Telex machines were developed and produced world-wide by a variety of manufacturers. Most of these machines were compatible in one way or another. The initial machines worked at the rather low baud-rate of 45.45 baud or 50 baud, but later machines were capable of running at 75, 100 and even speeds up to 150 baud as well. The following manufacturers produced telex equipment:
 
  • ACEC
  • Creed
  • Gretag
  • Hasler
  • Lorenz (SEL)
  • Olivetti
  • OKI
  • Philips
  • RFT
  • Siemens
  • Teletype
  • Tekade
  • Transtel
References
  1. DF3OE's Fernschreiber Museum
    Teleprinter museum by Henning Treumann (German/English).

  2. TelexPhone project
    An initiative of Henning and Philipp in Germany.

  3. Fernschreibamt Hausneindorf
    Private teleprinter collection of Michael Brandes (Germany). Retrieved April 2012.

  4. ECMA, Standard ECMA-10 for Data Interchange on Punched Tape
    2nd Edition. July 1970.

  5. Wikipedia, Radioteletype
    Retrieved january 2014.

Further information

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Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Friday, 10 January 2014 - 10:58 CET
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