Teletex¶

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.

• Olympia Disque with IKBS
• Wandel Goltermann DTX-1

Network¶

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.

Relevant Specifications¶

• ITU-T F.200 (Teletex service)
• ITU-T T.61 (Teletex character set)
• ITU-T X.21 (interface)