10/100Base-T electrical isolation specification

I wish to know the specification that Ethernet adapter manufacturers should comply with regarding the electrical insulation/isolation between the data cable (RJ45 socket) connections and the Ethernet adapter circuitry earth.
Specifically the maximum permitted voltage and typical insulation resistance.
I am asking this question because the is an issue of un-reliable Ethernet comms between a local area network and a particular industrial control equipment (Omron) and one of the engineers has suggested that it might be an "Earth loop" problem.
Personally, I think that this is highly unlikely as there are several other industrial equipments on the same site that use the local area network without any problems and the eqipments are earthed quite well.
the site uses Cisco Catalyst Ethernet switches model 3650G
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alcindorAsked:
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CompProbSolvConnect With a Mentor Commented:
According to page 339 of:
http://standards.ieee.org/getieee802/download/802.3-2008_section1.pdf
the spec (for 10baseT) is 25V ptp at 500kHz or lower

Page 491 of:
http://standards.ieee.org/getieee802/download/802.3-2008_section2.pdf
shows a similar spec for 10baseT
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Istvan KalmarHead of IT Security Division Commented:
Hi,

I advis to use optical patches, and you able to makre real isolation!
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alcindorAuthor Commented:
That does not answer my question.
I wish to know the electrical insulation characteristics of 10/100Base-T Ethernet adapters.
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Istvan KalmarHead of IT Security Division Commented:
if you afraid any earth loop problem you need to use optical connections with media converters!
Here is a data sheet:

http://www.blackbox.com/Store/Detail.aspx/Ethernet-Data-Isolator-10BASE-T-100BASE-TX/SP426A
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alcindorAuthor Commented:
I'm sorry but you still aven't answered my question.
I am not looking for a suggested solution to the problem.
I want to know the electrical insulation characteristics of the Ethernet circuits so that we can investigate and determine whether or not the differences in "Earth"potentials between the two equipments might be an issue.
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alcindorAuthor Commented:
Exactly what I wanted,  thanks for your help.

Roger
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