Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!mcvax!ukc!tcdcs!tcdmath!ch
From: ch@maths.tcd.ie (Charles Bryant)
Newsgroups: comp.dcom.modems
Subject: Re: Modems for Minitel ( 1200/75bps )
Summary: Can't use V.22 at 1200/75
Message-ID: <874@maths.tcd.ie>
Date: 7 Jun 89 17:20:27 GMT
References: <762@sbsvax.UUCP>
Reply-To: ch@maths.tcd.ie (Charles Bryant)
Organization: Maths Dept., Trinity College, Dublin
Lines: 17

In article <762@sbsvax.UUCP> emma@sbsvax.UUCP (Martin Emmerich) writes:
}In article <692@flatline.UUCP>, erict@flatline.UUCP (J. Eric Townsend) writes:
}> I'm looking for leads/pointers/sources of modems that will work
}> with the French Minitel (U.S. Videotel in the United States).  These
}> modems use a wierd 75bps one way/1200bps the other way protocol.
}
}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.

It is definitely not possible. The 1200/75 standard is V.23 (which is quite
popular in Europe). This uses a Frequency Shift Keyed modulation scheme. The
V.22 standard uses Phase shift modulation (same as Bell 212A).
-- 

		Charles Bryant.
Working at Datacode Electronics Ltd. (Modem manufacturers)