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From: GPWRDCS@gp.govt.nz (Don Stokes, GPO)
Newsgroups: comp.dcom.modems
Subject: re: Modems for Minitel ( 1200/75bps )
Message-ID: <630@gp.govt.nz>
Date: 26 Jun 89 12:49:27 GMT
References: <762@sbsvax.UUCP>
Organization: Government Printing Office, Wellington, New Zealand
Lines: 22

In article <762@sbsvax.UUCP>, emma@sbsvax.UUCP (Martin Emmerich) writes:
> Rumors say it would be possible to use a normal V.22 modem for split-speed. You
> only had to lengthen every bit into 16 bits ( = 1200 / 75 ) by software. But I
> never tried it. It is said that someone had done it sucessfully.

Not a prayer.  The modulations, carriers and baudrates are different.  
V22 actually runs at 600baud, two bits per baud using phase modulation.
V23 is normal FSK, at 1200baud. 

What you may have heard of is multiplying bits to produce a 75bps back 
channel for a V23 modem on a DTE that does not support split speeds - 
although start and stop bits would complicate the issue more than 
slightly - it would be like communicating over a noisy line.  Remember 
that there are 10 bits to a transmitted byte (assuming 8 bits, no parity 
or 7 bits with parity, and one stop bit).

Don Stokes, Systems Programmer    /  /   Domain:                  don@gp.govt.nz
Government Printing Office,      /GP/   PSImail:          PSI%0530147000028::DON
Wellington, New Zealand         /  /   UUCP:  ...!munnari!vuwcomp!windy!gpwd!don
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