Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!motcsd!hpda!hpcuhb!hp-ses!hpdml93!stephen
From: stephen@hpdml93.HP.COM (Stephen Holmstead)
Newsgroups: comp.sys.amiga
Subject: Re: 9600 bps Modems
Message-ID: <380027@hpdml93.HP.COM>
Date: 5 Jul 89 15:18:01 GMT
References: <11167@mcdphx.phx.mcd.mot.com>
Organization: Hewlett Packard - Boise, ID
Lines: 44

Sorry to eat up bandwidth, but I just had to jump in and make a
correction.  People seem to always make a mistake when talking about
modem speeds.  For example,

>  I understand the 'standard' for 9600 baud is between the U.S. Robotics
                                        ^^^^
It is IMPOSSIBLE to have a 9600 _baud_ modem work on the telephone lines.
However, a 9600 _bps_ modem IS possible.  I know the distinction is
minor, but since people continue to make the mistake, I want to clarify.

_bps_ refers to "bits per second" in the transfer rate.  This is how
just about ALL communication links are rated.

_baud_ refers to "symbols per second" in the transfer rate.  In older
modems (ie. 1200bps, 300bps, etc), each symbol comprised one bit worth
of data (one frequency was used to represent a ZERO and another was used
to represent a ONE).  Thus, 1200 baud equals 1200 bps.  However, when 
people began increase the transfer rate, it only worked when there was a 
direct connection.  However, when trying to use the telephone system, 
the maximum transfer rate is about 2400 baud.  This is due to the 
multiplexing done on the telephone lines.  It sounds like when you are 
talking on the phone that you have a continuous connection, but in 
reality, you are being "time-sliced" with other conversations.  So with 
higher transfer rates, symbols would be lost in the "switches".  
Therefore, people began sending more bits per symbol.  People began 
using multi-phase and multi-amplitude frequency codes to send 2, 4, or 
8 bits per symbol.  Thus, they could get 2400 bps, 4800 bps, and 9600 bps 
while only sending at 1200 or 2400 baud.

So, when you buy a 9600 bps modem, it will really only transmit at 1200 
or 2400 baud (depending on the implementation).  Thus, it is a 9600
_bps_ modem and NOT a 9600 _baud_ modem!

Again, sorry to eat bandwidth, but I hope that everyone learned
something.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Stephen Holmstead
...!hplabs!hpdmlge!stephen                      //
Hewlett Packard Disk Memory Division          \X/  Amiga Forever!
(208) 323-2840

I remind you that humans are only a tiny minority in this galaxy.
	-- Spock, "The Apple," stardate 3715.6.