Path: utzoo!mnetor!uunet!husc6!bloom-beacon!mit-eddie!uw-beaver!tektronix!reed!douglas
From: douglas@reed.UUCP (P Douglas Reeder)
Newsgroups: comp.sys.apple
Subject: Re: GS Serial Port
Message-ID: <8945@reed.UUCP>
Date: 21 Apr 88 19:50:49 GMT
References: <8804192242.AA27374@wpi.local>
Reply-To: douglas@reed.UUCP (P Douglas Reeder)
Organization: Reed College, Portland OR
Lines: 16
Keywords: RS232

STANDARD RS-232 (which no one seems to follow) calls for balanced pair
transmission (data pulses are sent out as positive pulses on the + lines
and negative on the - lines).  The signal is recieved with a differential
amplifier.  This improves transmission quality as any noise imposed is
imposed on both lines and ignored by the differential amplifier. 
This setup is neccesary when you run cables on the order of 100m.  Since
microcomputer cables are seldom more than a few feet, everyone cheats on 
the standard and there's seldom a problem.
    If you need transmission over longer distances than 232 can do, there are
other standards with different rquirements.

-- 
Doug Reeder                           USENET: ...!tektronix!reed!douglas
10 Cyclopedia Square             from BITNET: douglas@reed.UUCP
Terminus City                     from  ARPA: tektronix!reed!douglas@berkley
Terminus,The Foundation               Box 502 Reed College,Portland,OR 97202