On Sep 20, 1996 at 18:38, Kris Roebuck of 3:690/426 wrote:

 KR> Could someone explain to me the difference between baud rates and bps.

I'm a little rusty on this, but as I recall...

In short, "baud" refers to signal changes per second
(electrically), whereas "bps" is bits per second, the amount of
digital information per second that is being transmitted.

In times past, baud was essentially the same as bps numerically, since the
number of signal changes per second matched the number of bits per second. 
Now, it's harder to squeeze more signal changes per second out of the
telephone network, so they have to encode more bits to each signal change,
so the "bps" rate goes higher than the "baud" rate.

In recent Rockwell documentation you may have noticed (posted in here, as I
recall) that they're starting to use "symbol rate" instead of
"baud rate" simply because "baud" has become
contaminated by general usage (typical!) so that many people now think that
"baud" and "bps" are identical terms (they're
technically, *not* identical).

 KR> I'm told that they have different meanings, but no-one will tell me why.

As above - many people are lost in the "baud equals bps" myth. 
Most people say "baud" when in reality, they're talking about
"bps".  Few people know, need to know or even care what
"baud rate" a particular connection is functioning at - most
people just need to know the "bps rate".

 KR> Secondly, this new 56kbps modem from Rockwell (and their 
 KR> associates)...why a split rate?

Simple - they couldn't quite get their tricky techniques to work in both
directions.  ;-)

 KR> Why recieve at 56k and send at 33.6?  I thought we gave up
 KR> the idea of split rate modems ten years ago.

Back then, the split-speed modem served a particularly purpose, for on-line
services where you were receiving more than you sent.  The new 56Kbps
modems are being pushed with the same philosophy - that is, you receive
more than you send.  On the upside, the alternative channel will probably
be up to around 33.6Kbps anyway, so that's not too shabby.

Cheers..


    - dave
    d.begley{at}ieee.org

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