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From: howard@COS.COM (Howard C. Berkowitz)
Newsgroups: comp.dcom.modems
Subject: Re: baud vs. bit/sec.
Message-ID: <214@cos.COM>
Date: Thu, 23-Apr-87 08:01:18 EST
Article-I.D.: cos.214
Posted: Thu Apr 23 08:01:18 1987
Date-Received: Sat, 25-Apr-87 09:32:05 EST
References: <8704220426.AA03311@ucbvax.Berkeley.EDU>
Organization: Corporation for Open Systems, McLean, VA
Lines: 52
Summary: BPS=baud if digital Eye patterns



The previous article made some excellent points on the confusion 
between baud and bits per second.  While I agree the "consumer"
should exclusively use BPS/K[ilo]BPS/M[ega]BPS (and always spell
out bytes per second), there is at least one place that knowing
the true analog baud rate can be useful:  generating "eye"
patterns.

An eye pattern is an oscilloscope display which gives an idea
of total system transmission quality.  Sales strikes again here,
for most commercial "eye pattern generators" actually are
constellation or phasor displays.  For my purposes, eye patterns
are NOT the neat geometric displays of dots (probably more
useful than eye patterns) which the diagnostic sections of 
good high-speed modems can produce.  Eye patterns look like
they came out of a science fiction movie, and are good
1) for impressing management and visitors amd 2) getting
a visual go-no/go check if you have no other equipment.

Eye patterns are generated with an oscilloscope, using the signal
on the line and the baud rate as the sweep rate.  Baud, in this
context, is defined as the number of times per second the line
changes state.  With this setup, you will see a number of overlapping
more-or-less sine waves, which in their crossing produce a central
empty "eye," something like the eye of a hurricane.  The larger
the eye opening, the better the transmission performane.

This is basically for entertainment, although it is useful in
some engineering applications.

One point about the previous article -- I never thought before to
use the rule that it's bps on the digital side and baud on the
analog, and borrow it with gratitude as a teaching device.
To be technical, though, baud=bps on the digital side, because
there is one signal state change per bit on a digital channel.

Randy's article was excellent for the consumer of modems.

......

"Consumers" of modems remind me of a note rumored to have generated
the largest letter-writing campaign in the history of one IEEE
magazine.  We have, for a long time, tacitly understood that a
Consumer of Single Socks lived in washing machines.  The pubished
note suggested this belief was wrong.  It proposed that Socks are
the immature but sexual form of the Wire Coat Hanger.  Have you
ever noticed how wire coat hangers multiply?  This is due to
one member each of two sock pairs (i.e., of different sock sexes)
mate to form a wire coat hanger.  The divorced partners of these
socks are too shaken to mate (or afraid of incest), and thus become
the odd socks in the drawer.