V.23 protocol

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Mon Dec 6 21:56:30 1999

On Dec 6, 18:21, Jean-Pierre Hofer wrote:
> I am looking for specifications of the old V.23 protocol, or general
> informations about this.

It's a CCITT modem standard for half-duplex asynchronous communication at
600 or 1200 baud (one direction, on the forward channel) with a 75 baud
back channel. Because the back channel is not just used for signalling, it
somtimes used to be called "asymmetric duplex". It's an FSK system, the
forward channel uses 1300Hz/1700Hz tones for 600 baud, or 1300Hz/2100Hz
tones for 1200 baud; the back channel uses 390Hz/450Hz. The lower
frequency is used for MARK and the higher for SPACE.

The standard also specifies the answer tone frequency (2100Hz) and some
timing but I can't remember the details.

Pete						Peter Turnbull
						Dept. of Computer Science
						University of York
Received on Mon Dec 06 1999 - 21:56:30 GMT

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