Teletex

The teletex service was an internationally standardized text communication service for the transmission of texts with a speed of up to 2400 bit / s The transmission network in Germany the technique of Datex -L, Datex -P and ISDN was used. The teletex service was an evolution of telex, telex service and with this largely compatible.

Instead of the 5 -bit telex character set that knows no difference between uppercase and lowercase letters, a 332 characters comprehensive, illustrated in 8 bits character set was used, with which you can write all common languages ​​in Europe correctly, the imposing time (1981 ) used the Latin alphabet. From the ISO that font was standardized as ISO 6937, CCITT CCITT T.61 ITU as.

History

Teletex (abbreviation: Ttx ) should generally replace the telex service that was not up to date quickly with about 50 bit / s. Teletex terminals were an association of electronic telex and typewriter in one device. In Germany the service of the Federal Post Office 1981 was introduced and set in 1993 again. In early 1986 there were in the Federal Republic of Germany around 12,600 teletex participants. With a teletex Telex converter ( TTU ) of the service transition for message transfer between teletex and telex connections was possible. This means that from a telex or teletype unit of messages to a teletex device could be sent and vice versa.

The teletex service has not been enforced for several reasons on the market:

• The specialized Teletex typewriters were expensive. Instead of these devices is increasingly translated by PCs. These PCs or intermediate receiving boxes but had to fulfill, such as day and night to be accessible, making this variant expensive high demands.
• Fax devices made ​​it possible to transmit any message as a picture. This fell off the limitations of the character set. It could be delivered Existing (including forms and brochures) and it had nothing to be typed. The units were affordable, faxing became the standard in the business and was also used by those who had never bought a teletype.
• From the late 1980s, the e-mail began its triumphal as a communication tool, yet hesitant, but from the beginning of the 1990s in wide use. It meant much lower costs and equipment expenses compared with Teletex and rapidly increasing functions such as file attachments even to sound and video ( the Commodore Amiga since 1986 was as a " multimedia computer " in the sale ), which Teletex could not offer.

Teletex terminals

The most widely used teletex terminal in Germany was with several thousand units, the T4200 of Siemens AG. The unit combined the functions of a normal typewriter, a memory typewriter with removable storage and screen, a teletex terminal and a remote recorder.

The Commodore also released a Teletex -enabled system from a Commodore computers, a junction box with built-in control computer, a specially advanced text processing and a revised Typenraddrucker CBM 8229 in Germany. The sales figures did not even reach 20, and the project was soon discontinued.

Teletex terminals are standardized in CCITT recommendation T.60.

Differences between Teletex and the telex service

The concept of the teletex service saw the following features before:

• Instead of Telex character set ( Baudot code) Teletex character set has been defined, the texts could properly present in practically all European languages. Unlike in 8859 as defined in ISO family of 8 -bit character sets, which provide a different encoding for each group of languages ​​, see the Teletex character set T.61 total of 14 combining characters before that cause no feeding the writing position, so that the The following characters with diacritical marks this is combined. Thus, a total of 332 characters represents.
• Teletex -enabled typewriters could have screen editing capabilities and caching, and automatically send the teletex messages to defined points in time. You could get the form of a typewritten letter, which the telex service was not possible.
• The teletex messages were sent at a much higher transfer rate than the telex messages. Teletex devices could send and receive each other at a speed of 2400 bit / s. This corresponded to the transfer of an A4-size page in about 10 seconds.
• The error rate was a factor of 10 better than the telex service.

• Telecommunications ( Germany )
• Communication technology