Re: Baud vs. BPS (Re: disk transfer methods)

[CUTblakeney@home.com (Jeff Blakeney)]

On 23 Aug 1999 02:39:27 GMT, wbdesnoy@acs2.acs.ucalgary.ca (Byron
Desnoyers Winmill) wrote:

>I have a vague idea of how baud and bps work with modems, but it is clouded
>by years of disuse.  :-(  If anybody has a moment, I would appreciate what
>(if any) role baud has with serial ports.

According to the Glossary of the book "Understanding Data
Communications" by George E. Friend, John L. Fike, H. Charles Baker
and John C. Bellammy, published by Howard W. Sams & Co., ISBN:
0-672-27019-6:

"Baud:  A unit of signalling speed equal to the number of signal
events per second.  Not necessarily the same as bits per second."

and

"bps (bits per second):  A measure of the information transfer rate of
a data channel."

Put in layman's terms with a little better explanation.  Bits per
second is simply the number of bits that are transmitted in one
second.

Baud is the number of times the transmitted signal changes per second.
In the case of a serial port, baud will always equal bps.  However,
baud is almost never used when discussing serial port transfer rates.

In the case of a modem, baud is the number of times the signal changes
per second but there can be more than one bit transferred with each of
these signals.  In the early days of modems, baud did equal bps but
that only lasted up to the 2400 baud modems as that is the highest
baud rate a standard telephone line can handle.  After this point,
modems started sending multiple bits with each baud signal thereby
multiplying the number of bits that were being sent each second.  2
bits per baud at 2400 baud = 4800 bps, 4 bits per baud at 2400 baud =
9600 bps.

The latest modems use different methods than earlier modems as well.

Suffice it to say that baud is pretty much an outdated term and
probably shouldn't be used at all anymore when talking about computer
communications.  Just stick with bits per second and you can't go
wrong.  :)

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