Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site ucbvax.BERKELEY.EDU
Path: utzoo!decvax!bellcore!ulysses!ucbvax!telecom
From: S.PAE@DEEP-THOUGHT.MIT.EDU (Philip A. Earnhardt)
Newsgroups: mod.telecom
Subject: RS-232 problem
Message-ID: <8603060705.AA05792@ucbvax.berkeley.edu>
Date: Tue, 4-Mar-86 14:16:02 EST
Article-I.D.: ucbvax.8603060705.AA05792
Posted: Tue Mar  4 14:16:02 1986
Date-Received: Thu, 6-Mar-86 22:19:25 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 20
Approved: telecom@xx.lcs.mit.edu

We have a noise problem with our RS-232 lines at work. We run pins 1,2, and 3
(with 7 shorted to 1)
for 2 lines in every office. Unfortunately, the 6 wires are run on a single
cable; the 2 lines are not shielded from each other. This still works OK
if someone has 2 terminals in their office or on terminals with multiple
ports. However, folks who use a T-switch to switch between their 2 lines
in their office will reliably send garbage down the unselected line.

Has anyone solved a similar problem? I'm guessing the what will 
is to put a load between pins 1 and 3 on the unselected line. To do this
automatically, we'd use a matrix switch instead of the t-switch:

Computer A ====== Terminal  *   Computer A ==  == Terminal
                            O                \/
                            R                /\
Computer B ====== Resistor  *   Computer B ==  == Resistor

Will this work? Am I in any danger of damaging our computer terminal
boards? Any estimate of an appropriate value for the resistor?
-------