Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!husc6!im4u!halley!rrt
From: rrt@halley.UUCP (Robert Teisberg)
Newsgroups: comp.sys.apple
Subject: Re: GS Serial Port
Message-ID: <353@halley.UUCP>
Date: 23 Apr 88 15:54:08 GMT
References: <8804192242.AA27374@wpi.local> <8945@reed.UUCP>
Reply-To: rrt@halley.UUCP (Robert Teisberg)
Organization: Tandem Computers, Austin, TX
Lines: 21
Keywords: RS232

In article <8945@reed.UUCP> douglas@reed.UUCP (P Douglas Reeder) writes:
>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).

I think you're describing RS-422 here.  RS-232 is an unbalanced
transmission protocol.  If you look at the RS-232 pinouts, you will see
that pin 7 is called Signal Ground (SG).  This is the return pin for ALL
signals in both directions.

Because it is unbalanced, RS-232 is limited to short cable runs at low
speeds and is vulnerable to noise. 

>-- 
>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


Bob Teisberg @ Tandem Computers, Inc.
...!ut-sally!im4u!halley!rrt