V.23

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V.23 modem of the Deutsche Bundespost (1985)
The same designs were also available under the designation 1200-05 (before 1992)

The V.23 standard is an early modem standard recommended by the International Telecommunication Union ITU-T in 1988 . It uses frequency shift keying to encode and transmit data with a maximum data rate of 1200 baud , half duplex at 1200 baud (mode 2) (or at a "fallback rate" of 600 baud, mode 1) for the data channel and an optional 75 baud auxiliary channel.

Three frequencies are defined for the 600/1200 baud data channel:

  • 1300 heart tone for binary 1
  • 1700 hearts (mode 1) or 2100 hearts (mode 2) for binary 0

For the 75 baud auxiliary channel, the frequencies

  • 390 hearts for binary 1
  • 450 hearts for binary 0

In some European countries V.23 mode 2 AFSK modulation (without auxiliary channel) is used to transmit the caller ID .

The V.23 standard was used for videotex and minitel, as well as screen text , among other things .

The Bell 202 modem defines a similar modulation scheme with different frequencies.

Interfaces

The interfaces required to control the modem are described in ITU-T recommendation V.24 .

Individual evidence

  1. ↑ Karl-Heinz Schmidt (Ed.): Terminals on the analog telecommunications network. Rev Deckers's Verlag, Heidelberg 1992, ISBN 3-7685-4889-9 , pages 313-318.

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