Quoting "Robert G. Brown" <[EMAIL PROTECTED]>, on Mon 28 Jul 2008
06:15:44 AM PDT:
On Mon, 28 Jul 2008, Eugen Leitl wrote:
On Sun, Jul 27, 2008 at 07:19:56PM -0700, Jim Lux wrote:
bear in mind that ordinary ethernet both coax and twisted pair is
galvanically isolated.
This is strange, because I've seen (small) sparks and received (mild)
shocks from both, in two different locations.
Ground loop. Very dangerous. You go first...;-)
rgb
Very odd.. I'd be looking for an outright short from the cables to
something (or, a LOT of capacitive coupling)...
After all, the twisted pairs are isolated at BOTH ends..
Now, there is Power over Ethernet these days.. Basically uses each
pair of wires as a single conductor (i.e. they feed the juice in at
the center tap of the isolation transformer) but, again, that
shouldn't be sparking/shocking.
As you say, http://www.apcmedia.com/salestools/FLUU-5T3TLT_R1_EN.pdf
claims Ethernet is immune, yet I've read somewhere that Gigabit ethernet
is more susceptible than Fast Ethernet. I've got (cheap) UPSen for
almost all equipment, maybe they're the problem and not the switching
power supplies.
In any case I'll have an electrician diagnose the problem. Unfortunately,
I anticipate his solution would involve pulling through a new
large-crossection
ground wire to several locations. It is at this point that lack of wall
conduits will become quite painful.
Nope.. shouldn't require a separate grounding conductor, at least not
along with your cabling.
What you might want to do is see if your electrical safety ground
(third pin/green wire ground) at the two ends is at a radically
different voltage. You might have a miswired receptacle.
You should be able to just drag a single conductor through the house
and use a multimeter to measure the voltage between the ground pins,
and it should be zero, or pretty darn close.. use the AC setting, and
put a small (few K) load resistor across the meter, so you don't get
fooled by electrostatic/electromagnetic coupling... which will induce
several volts, at least into an open circuit.
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