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From: jbn@glacier.UUCP
Newsgroups: net.lan,net.dcom
Subject: Re: Do you ground your Ethernet cable?
Message-ID: <7584@glacier.ARPA>
Date: Sat, 17-May-86 21:53:54 EDT
Article-I.D.: glacier.7584
Posted: Sat May 17 21:53:54 1986
Date-Received: Fri, 23-May-86 07:52:39 EDT
References: <261@pedsgo.UUCP>
Distribution: net
Organization: Stanford University, IC Laboratory
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Xref: watmath net.lan:1494 net.dcom:1927
Summary: Grounding of Ethernets


       The Ethernet I spec called for the outer conductor of the Ethernet
cable to be ungrounded.  Because the connectors are uninsulated, this
created a safety hazard (a short to the braid due to wear between two
rubbing cables, one Ethernet and one power cable would
electrify all the exposed Ethernet connectors but wouldn't blow any breakers) 
and violates the U.S. National Electrical Code.  So the Ethernet II spec 
calls for grounding the Ethernet at exactly one point.
       Back at Ford Aerospace, we grounded our Ethernet with a copper
strap brazed to one of the connector barrels; the copper strap connected
to the building ground system (3/8" x 1.5" copper busbars under the
raised floor tied via heavy copper cable to the grounding rods out back
of the building and cross-connected to power system ground at the wye
of the main transformers; overkill, but a place that builds antennas
takes a dim view of RF noise.)

						John Nagle