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Posted by Robert Redelmeier on February 1, 2006, 11:01 am
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> Point by Robert Redelmeier is important. One building can become
> a lightning rod that conducts direct lightning strikes through
> all network interfaces in the other building. Technology well
> proven even before WWII and that is standard in every telephone
> switching station. All utility and communication cables must
> leave at a common service entrance so that each protector makes
> a short connection to the common earth ground. Where does
> AC electric and phone line enter the building? Where do both
> share a common earth ground? That is where an inter-building
> LAN cable must exit and enter so that each LAN protector makes
> a less than 10 foot connection to that single point earth ground.
Exactly! It gets even worse: A direct lighting strike to a building
is not required. Any nearby (100m) strike may elevate one building's
groundstake much more than another's. Then any direct conductive
connection becomes a new groundpath.
-- Robert
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