[clug] MythTV on TransACT

steve jenkin sjenkin at canb.auug.org.au
Fri Sep 1 07:19:08 GMT 2006

Sam Couter wrote on 24/8/06 9:48 PM:
> Mathew Meins <sys9000 at tpg.com.au> wrote:
>> Ethernet over UTP is no good for a situation like this. Each end of the
>> line will be at a different ground potential, resulting in current flowing
>> over the copper, which will probably let the magic smoke out of the line
>> drivers at each end.

A networking friend just finished 12 months working for a power
*generation* company.  He made the comment that around power stations
they paid particular attention to grounding and different earth
potentials... In the power stations, they only ever ground *one* end of
their cat5 cables - just what you're talking about.  He cited an example
where they had a run between buildings and had a very large notice on
the cabinet in the second building warning about the 'non local' ground...

He also mentioned that in a control room they ran fibre to near a PC and
then a copper-fibre interface to it (for the standard NIC).  They did
have to occasionally replace the NIC.


> This can happen with two computers in one building, or even one room. I'm
> pretty sure ethernet transceivers are galvanically isolated for just this
> reason. The days of coax used to be worse, with every machine on the
> segment connected to the same physical piece of wire instead of just the
> machine and the hub/switch.

Steve Jenkin, Info Tech, Systems and Design Specialist.
0412 786 915 (+61 412 786 915)
PO Box 48, Kippax ACT 2615, AUSTRALIA

sjenkin at canb.auug.org.au http://www.canb.auug.org.au/~sjenkin

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