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From: dixon@gumby.paradyne.com (0000-Tom Dixon(0000))
Newsgroups: comp.dcom.lans
Subject: Repeaters Grounding Thin Ethernet coax lines.
Message-ID: <6638@pdn.paradyne.com>
Date: 8 Oct 89 17:26:53 GMT
References: <3824.25292578@zeus.unl.edu> <2128@avsd.UUCP> <27682@amdcad.AMD.COM>
Sender: usenet@pdn.paradyne.com
Reply-To: dixon@gumby.paradyne.com (0000-Tom Dixon)
Organization: AT&T Paradyne, Largo, Florida
Lines: 30

In article <27682@amdcad.AMD.COM> rpw3@amdcad.UUCP (Rob Warnock) writes:
>You know, that actually brings up a good question. Repeaters SHOULDN'T
>ground the cable on either side, but *a* ground for each thin Ethernet
>must come from *somewhere*, and I doubt that most network installers
>think to provide one. [It may be the case that these multi-thinwire
>repeaters ground the "down leg" thinwires to their own chassis ground,
>which would be the right thing to do in most cases assuming the chassis
>ground is connected to the third or "green" wire, but they should never
>ground the "up leg", i.e., the trunk or backbone connection.]

But what about backbone thinnet segments?  This means that a thinnet
segment that runs from repeater to repeater would be a gound loop.  
This is not good.

The Cabletron 8 port repeaters we use have 8 thinnet ports and 1 AUI
port.  I would assume that we should hook backbone thinnet to a 
non grounding transciever and hook that to the AUI port on the 
repeater.  We presently are using the thinnet ports as you expect. 

Do any vendors make repeaters that have configurable ports that can
either be grounded or not?

Rob, Thanks for the brain food.  I had not even thought of this before.

>Rob Warnock
>UUCP:	  {amdcad,sun}!redwood!rpw3

Tom Dixon
AT&T Paradyne
uunet!pdn!dixon