[c-nsp] T1 Cables

[Janet Plato]

DS1 cabling does not use the normal USOC pairing, so you forgo
common mode rejection of noise.  When a signal pin and that
signal's ground share a common path with normal spacing, for
example in a single twisted pair, they pick up the same amount of
noise from the environment.  The noise is common to both wires,
and since the receiver is expecting to see the signal expressed as
a difference in voltage between signal pin and ground pin, not
an absolute voltage difference, the noise that is common to both
wires is rejected.

Having said that, I've run T1 short distances in a normal data
center environment on some really crappy wire without problems.
I suspect you either have a problem not related to your cabling,
or enough noise that you really need the common-mode noise
rejection afforded by correct pairing.

I do not have a source of such cables, I've not used such things
in a long time.

Hope this helps,

Janet Plato

On 5/18/07, Vincent Aniello <vincent.aniello at pipelinefinancial.com> wrote:
> Are there cables specifically for use with T1s that we should be using
> to connect circuits to our Cisco routers with integrated CSU/DSUs?  We
> currently use CAT5E cables and have chronic problems with errors on a
> few of our circuits.  The cable length between the smart jack and router
> is 25 feet.
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> Thanks.
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> V/
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