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From: sonny@charybdis.harris-atd.com (Bob Davis)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Baud vs. bps.
Message-ID: <4194@trantor.harris-atd.com>
Date: 26 Aug 90 23:57:59 GMT
References: <849@idcapd.idca.tds.philips.nl> <4188@trantor.harris-atd.com> <5001@pegasus.ATT.COM>
Sender: news@trantor.harris-atd.com
Reply-To: sonny@trantor.harris-atd.com (Bob Davis)
Organization: Advanced Technology Dept., Harris ESS, Melbourne, FL
Lines: 44

In article <5001@pegasus.ATT.COM> dmt@pegasus.ATT.COM (Dave Tutelman) writes:
[Stuff deleted]
>In article <4188@trantor.harris-atd.com> sonny@trantor.harris-atd.com (Bob Davis) writes:
[Deletions]
>>	THE BIT RATE *ALWAYS* IS EQUAL TO THE BAUD RATE TIMES THE
>>	NUMBER OF INFORMATION BITS CARRIED PER BAUD TIME BY THE MODEM.
                  ^^^^^^^^^^^^^^^^  
>
>Close, but not quite. 
>Lex's original speculation covers "the rest of the story".
>
>A "bit" is a unit of information.  Start and stop pulses (frequently
>and inaccurately called start and stop bits) are really transmission
>related synchronizing signals, not information.  The "old" modems
>Bob describes actually had a bit rate LESS than the baud rate.
>
>Dave
YOU ARE RIGHT, DAVE, but...
	Above, I stress "INFORMATION BITS" as being important. For
the old modems which have the overhead of synchronization bits, as
well as for newer techniques which  have the overhead of redundant
bits necessary to support error-correction coding strategies, I would
say that the INFORMATION BITS carried per baud is reduced below the
raw channel bits per baud. For example, in the old schemes using
1 start bit, 8 INFORMATION BITS, and 1 stop bit, I would say that
the INFORMATION BITS per baud is equal to 0.8. This is because
only 8 out of every block of 10 bits bears INFORMATION.
	Similarly, if a rate one-half error correction code is
used on one of the newer schemes, I would say that the INFORMATION
BITS per baud is one-half the raw channel bits per baud.  
	Therefore, I stand by the statement:

	THE BIT RATE *ALWAYS* IS EQUAL TO THE BAUD RATE TIMES THE
	NUMBER OF INFORMATION BITS CARRIED PER BAUD TIME BY THE MODEM.
                  ^^^^^^^^^^^^^^^^

Peace,

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