[154958] in North American Network Operators' Group
RE: Managing free pairs to prevent DSL sync. loss
daemon@ATHENA.MIT.EDU (Matlock, Kenneth L)
Tue Jul 17 13:17:01 2012
Date: Tue, 17 Jul 2012 11:16:07 -0600
In-Reply-To: <79774.1342539500@turing-police.cc.vt.edu>
From: "Matlock, Kenneth L" <MatlockK@exempla.org>
To: <valdis.kletnieks@vt.edu>,
"John Souvestre" <johns@sstar.com>
Cc: NANOG Mailing List <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
-----Original Message-----
From: valdis.kletnieks@vt.edu [mailto:valdis.kletnieks@vt.edu]=20
> No, it will be strictly a DC current, with the amperage easily
calculated from the voltage difference between the two ends and the
resistance of=20
> however many cable-feet of wire is involved. Not usually a big deal,
unless your termination design didn't include the ability to sink a DC
current=20
> 24/7.
> (Of course, actually measuring the voltage and resistance may be
non-trivial :)
That brings up an interesting question. I assumed the ground potential
stays the same between 2 points, but have there been any studies to see
if it's actually DC, or if there's an AC component to it?=20
If there's an AC component in the ground at either end (or both) that
may introduce EM into adjacent pairs across the cable. And are they more
or less than the EM ungrounded pairs would pick up?
Ken Matlock
Network Analyst
303-467-4671
matlockk@exempla.org
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