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Re: fast ethernet limits

  • From: Stephen J. Wilcox
  • Date: Tue Jan 14 07:38:13 2003


> > Maybe they do it differently in the EU, but fire safety is also a concern
> > to me.
> 
> If you have potential differences like these the house needs a new
> electrical grid. Wait, that means that the entire North American continent
> needs rewiring ;-) Anyway, the mains PE MUST be made the best path home,
> and in a fail-safe manner. 
> 
> > Thank you, but I'll ground nearest to the earth, common bonded point. Its
> > served me well over the years.
> 
> Look at the emissions that manage to get into a star grounded, one point
> only system vs emissions bounced off a mesh grounded system with a decent
> EMC testing rig and repeat that phrase afterwards ;-)

I thought earthing one side of a shielded cable (be it Cat5, or any other
type) was actually part of electrical regulations. (maybe I just assumed that as
a result of practice)

It is a known fact that earth varies within buildings, and from place to place
in the ground, this is nothing to do with faulty wiring in houses or fault north
american continent, this is a simple chemical/physical phenomenon as a result of
subtle changes in water tables, salt, minerals etc 

So this means there is a difference in potential from point to point - thats
voltage to you and me. So if you connect both of these together you get a flow
of current - not good..

Of course, when you ground one end it also means you should be careful when
working at the other end not to touch the shied as you are earthed to local
ground and it may therefore have a live voltage should you touch it.

Steve






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