Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!rh1m+ From: rh1m+@andrew.cmu.edu (Rudi Jay Halbright) Newsgroups: comp.dcom.lans Subject: Re: Grounding Ethernet coax lines. Message-ID: Date: 11 Oct 89 01:50:11 GMT Organization: Social and Decision Sciences, Carnegie Mellon, Pittsburgh, PA Lines: 41 childers@avsd.UUCP (Richard Childers) writes: >rpw3@amdcad.UUCP (Rob Warnock) writes: >>Wrong. A given Ethernet (thick or thin) *must* be grounded *EXACTLY ONCE*, >>no more, no less. To do other wise can *increase* your noise problems or >>even -- are you ready for this? -- melt your cable! >Hmm. The thin ethernet cables I'm familiar with all have two ends. Neither >end is distinguished from the other. Both have the coaxial braid firmly >attached ( grounded ) to the connector ... I don't see how you could only >ground it ONCE. It has to be connected to two devices. >>Remember, the original question was talking about between buildings. I have >>seen situations where there are MANY [is >10 many enough?] volts difference >>between two adjacent buildings, and if you ground an Ethernet at both ends >>you have just attempted to short out that potential difference. >I can see how that might be a problem, but that would seem to require that >the equipment be grounded, separately. ( In any case, I don't think ethernet >belongs between buildings, I think that's a job for fiber optic. ) >>... "As designed" there is *NO* ground! Which is correct! [detail removed] It seems that you're confusing grounding with shielding and the connector attached to the shield wire with "ground". Grounding means attaching to earth ground. This can be either a pipe which is properly grounded or to the third prong on a three prong outlet, ideally the outlet should be tested to make sure the ground pin is properly wired to earth ground and that is not live (i.e. shorted to one side of the power line). In using thin ethernet, one end of the network should be connected to earth ground. The way I do this is to run a wire from the shield of one of the terminating resistors to ground. Simple testors are available to check if ground is properly wired, these are available from many electronics supply houses, including Radio Shack. -Rudi Halbright rh1m@andrew.cmu