Thanks Brian. That explains a lot. I thought it was somewhat odd that most ethernet magnetics provide much greater isolation than required by the safety standard. My thinking was it was for use in a greater range of applications and maybe even for use where the Norway/Sweden deviations apply, but that didn't make since because the parts only had a hipot rating and not supplementary insulation with a stated creepage/clearance figure.
So, based on the info you've given, it seems there are a certain number of ethernet products out there that may not conform to all of the IEEE specs. (I'll keep make/model notes on testing I do in the future)
The history on this is that the prototype 3 megabit Ethernet at Xerox PARC encountered around 90 volts differential in ground potential from one part of the building to another. That was problem.
![[Linked Image]](https://www.electrical-contractor.net/ubb/smile.gif)
So when we wrote the spec for the 10 MB Ethernet, which could have coax segments spanning distances of as much as 500 meters, we made sure that we were adequately covered for differences in ground potential.
It would appear that subsequent revisions of the standard have retained this philosophy.
[This message has been edited by SolarPowered (edited 12-21-2006).]
