In article ,
John Stumbles wrote:
You should not use copper for data links between buildings. If
you've got separate electrical supplies you may have enough
potential difference between ends to exceed the common-mode
rejection of the ethernet receivers and cause data problems.

Wonder how broadcasting got round this in the old days - all lines between
building were copper. And indeed around the country. Of course most of
these lines were fed via a balancing transformer which would provide low
voltage isolation - but certainly not from high voltage or lightening. And
I'd guess later equipment used electronic balancing.

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Dave Plowman London SW
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