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From: rab@WELL.UUCP (Bob Bickford)
Newsgroups: mod.telecom
Subject: Re: RS-232 problem
Message-ID: <8603110520.AA05941@ucbvax.berkeley.edu>
Date: Sat, 8-Mar-86 23:02:16 EST
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Posted: Sat Mar  8 23:02:16 1986
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   Methinks you should not tie pins 1 and 7 together.  Just leave pin 1
completely out of the connection; it's only a frame ground and if you're
in the same building you don't need it.  We don't use it!

   Most T-switches do *not* switch the pin #1 connection, so there may
be the source of the trouble:  they're always tied together.

   The resistors should go to a 12v reference, not to ground, although
ground will work with many receiver IC's.  I would expect there is
already a resistor in the interface PCB, going to 12v, and if you
added one to ground at the switch you'd get a tendency to float to 6v,
maybe leading to more noise than you have now.  (assuming you use the
same value, namely 10K ohms)