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From: steckel@alliant.UUCP
Newsgroups: comp.dcom.modems
Subject: Re: baud vs. bit/sec.
Message-ID: <487@alliant.UUCP>
Date: Wed, 22-Apr-87 13:12:29 EST
Article-I.D.: alliant.487
Posted: Wed Apr 22 13:12:29 1987
Date-Received: Sat, 25-Apr-87 04:07:28 EST
References: <8704220426.AA03311@ucbvax.Berkeley.EDU>
Reply-To: steckel@alliant.UUCP (Geoff Steckel)
Distribution: world
Organization: Omnivore Technology, Newton, MA
Lines: 24
Keywords: baud rate bit rate
Summary: BAUD does indeed mean a lot

BAUD = signalling elements per second
BITS per SECOND = data bits per second

Any ASYNCHRONOUS communications device on RS232 or RS422/423 has start and
stop bits attached to each and every character transmitted; these are required
for the devices on each end of the line to detect where the data characters
live.  Typical amounts are:
  ancient technology @ 110 baud: 1 start bit, 8 data/parity bits, 2 stop bits
  wrong-headed technology @ 134.5 baud: 1 start bit, 5 data bits, 1.5 stop bits
  newer technology @ 300 baud & up: 1 start bit, 8 data/parity bits, 1 stop bit

These start & stop bits are transmitted (for instance) from terminal to host,
over low speed asynchronous modems, etc.  In these cases BAUD is the correct
term to use to determine signalling speed.  Bits per second will always be
lower, but it is format and user dependent.

SYNCHRONOUS communications does not use start and stop bits; it uses sync
patterns at the beginning of a block to co-ordinate the sender and receiver.
Again, the BAUD rate is the signalling rate over the channel, while the
data rate depends on the size of sync pattern, block header and trailer,
etc., etc., and is format and user dependent.

I hope this clears up the confusion.
	geoff steckel (steckel@alliant.uucp, gwes@wjh12.uucp)