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From: jqj@cornell.UUCP
Newsgroups: net.lan
Subject: ground reference on Ethernets
Message-ID: <403@cornell.UUCP>
Date: Tue, 21-Aug-84 07:34:48 EDT
Article-I.D.: cornell.403
Posted: Tue Aug 21 07:34:48 1984
Date-Received: Wed, 22-Aug-84 01:31:48 EDT
Sender: jqj@cornell.UUCP
Organization: Cornell Univ. CS Dept.
Lines: 16

From: jqj (J Q Johnson)
Cornell Engineering is in the process of designing a large  Ethernet
configuration spanning 10 buildings on the Cornell campus.  Our plan
is the traditional 500m backbone, with repeaters in each building
connecting to an in-building segment.  Concern has recently been raised
about the differences in ground reference potential between buildings.

Does anyone out there know whether differences in ground reference between
two different controller/transceivers on an Ethernet are likely to cause
degradation in the network?  What is the maximum allowable difference
in ground reference?

My Blue Book does not discuss this issue directly, though some of the
discussion (notably sects. 7.6.3, 7.4.3 and 7.2.4) leads me to believe
that a moderate difference in ground might be acceptable.  Anyone out
there have experience or advice?