Teletex is a mostly-forgotten technology somewhere between Telex and Telefax:
  • like Telex, it transmitted data as characters
    • however, Teletex supports a more complete alphabet with lowercase characters and special characters (Telex: Only 5-bit uppercase)
  • like Telefax, it transmitted formatted entire pages/documents
    • however, Teletex transmits the text characters and their formatting (Telefax: A raster-pixel-image).

Teletex was invented aroud 1981. German operation was from 1981 through 1993.

Terminal Devices

Early/Simple Teletex devices are typically built from pre-existing daisy-wheel typewriters with single-line memory/editing/display capability. Those typewriters were extended with additional communications hardware and software in order to receive and/or transmit in Teletex format.

Later, more complex Teletex devices were text/word processing systems, either dedicated or in the form of personal computers. Those were then likewise extended with a Teletex communications hardware + software.


Teletex is designed to use a CSPDN (circuit-switched public data network). The Teletex user equipment interfaces to the network via a 2400 bps synchronous X.21 interface.

ITU specifications also specify operation of Teletex over PSPDN, PSTN or ISDN networks, but it is not known if any of this was ever deployed anywhere.

Communications protocol (stack)

  • X.21 is used as physical layer (synchronous 2400 bps)
  • X.21 is used for CSPDN signaling, i.e. for dialing the call
  • once the transparente bit-synchronous 2400bps channel is established via X.21, the following protocols are spoken (from bottom to top):
    • X.75 SLP in HDLC framing with parameters as per T.70 section
    • T.62 session layer
    • T.62 document layer

Relevant Specifications

  • ITU-T F.200 (Teletex service)
  • ITU-T T.61 (Teletex character set)
  • ITU-T T.62 (Session and Document layer)
  • ITU-T T.70 (Transport layer profile)
  • ITU-T X.75 (Transport layer)
  • ITU-T X.21 (interface)


  • Kapitel 9 von Eckart Giese, Klaus Görgen, Dr. Elfriede Hinsch, Günter Schulze, Dr. Klaus Truöl: Dienste und Protokolle in Kommunikationssystemen; 1985, Springer, Berlin/Heidelberg
  • Rolf Rüggeberg: Telefax und Teletex in nachrichten elektronik + telematik (net), Heft 12, Dezember 1982, S. 526-529
  • Peter Mogdans, Burkard Berning: Teletex - Ein neuer Fernmeldedienst der Bundespost; 1983, Unterrichtsblätter Jg. 36/1983 Nr. 9 S. 355-364
  • Frithjof Kroemer: 50 Jahre Telex in Deutschland; Unterrichtsblätter Jg. 37/1984 Nr. 3 S. 88-114
  • Franz Müller: Teletex-Dienst und Teletex-Endeinrichtungen; Unterrichtsblätter Jg. 40/1987 Nr. 6 S. 191-202
  • Richtlinie FTZ 111 1 R 293 1, Rahmenwerte für Teletex-Endgeräte, Deutsche
  • Schenke, K.: Textkommunikationsdienste für das Büro, Bundesministerium für das
    Post- und Fernmeldewesen
  • Müller, F.: Teletex - Technik der Endeinrichtungen, Sonderdruck aus fernmelde-
    praxis, Heft 22 u. 23/1985
  • Hans Dieter Hellige: GENESE UND NIEDERGANG VON TELETEX: LEHREN AUS EINER GESCHEITERTEN REVOLUTION DER BÜROKOMMUNIKATION ; Gekürzt erschienen in: H. Kubicek, G. Müller, E. Raubold, A. Roßnagel (Hrsg.), Jahrbuch Telekommunikation und Gesellschaft Bd. 2, Heidelberg 1994, S. 22-35

Updated by laforge 6 months ago · 9 revisions

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