V.23
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
- ↑ Karl-Heinz Schmidt (Ed.): Terminals on the analog telecommunications network. Rev Deckers's Verlag, Heidelberg 1992, ISBN 3-7685-4889-9 , pages 313-318.