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From: jbn@wdl1.UUCP
Newsgroups: net.dcom
Subject: Re: Having trouble with a cable under a
Message-ID: <207@wdl1.UUCP>
Date: Thu, 17-Jan-85 22:55:14 EST
Article-I.D.: wdl1.207
Posted: Thu Jan 17 22:55:14 1985
Date-Received: Mon, 21-Jan-85 04:38:18 EST
Sender: notes@wdl1.UUCP
Organization: Ford Aerospace, Western Development Laboratories
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Nf-ID: #R:fritz:-160000:wdl1:11700008:000:664
Nf-From: wdl1!jbn    Jan 17 18:53:00 1985


     There are all kinds of neat ways to get polyphase hum, but the real
question is whether the hum is common-mode or not.  If you short one end
of the line together and put an isolated scope across the other end, is
the hum unreasonable?  If not, all you need is some kind of short-haul
modem with good common-mode rejection.  You might even be able to get away
with sending RS-232 signals down the line if the devices at both ends
really implement the spec right, which calls for a -12 to +12 swing with
anything in the -3..+3 range ignored.  Just some RS-232 booster might be
good enough.  Get a Glasgal Communications catalog and look for something
suitable.