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From: bitar@ji.Berkeley.EDU (Philip Bitar)
Newsgroups: comp.dcom.modems
Subject: Re: What is Max speed possible on phone lines?
Message-ID: <21663@ucbvax.BERKELEY.EDU>
Date: Sat, 7-Nov-87 12:48:34 EST
Article-I.D.: ucbvax.21663
Posted: Sat Nov  7 12:48:34 1987
Date-Received: Tue, 10-Nov-87 02:00:09 EST
References: <KPETERSEN.12347581516.BABYL@SIMTEL20.ARPA>
Sender: usenet@ucbvax.BERKELEY.EDU
Reply-To: bitar@ji.Berkeley.EDU.UUCP (Philip Bitar)
Organization: University of California, Berkeley
Lines: 22
Summary: questions: baud rate, frequency, amplitude compatibility

Thanks to Keith Petersen for a detailed explanation of baud rate.
I would like to ask several more questions.
1. Baud rate
   From his msg:
   >...                                          The 2400 baud modems
   >common today use a form of QAM (quadrature amplitude  modulated).
   >...
   >QAM is the method used to get up to 9600  baud  out  of  a  phone
   >line. ...
   It is clear from the context that 2400 bps and 9600 bps are meant,
   where both bit rates are obtained using a baud rate of 600.

   Are baud rates other than 600 used?  If so, this would introduce
   another dimension of incompatibility, along with the alphabet or
   representation problem mentioned in the msg.

2. Frequency, amplitude
   Under QAM, frequency and amplitude could also be incompatible
   (unless there is automatic detection of them), so am I correct
   in assuming that these are standardized at 600 baud?  -- And that
   the phase jitter of 30 degrees refers to signals at the respective
   frequency and amplitudes?