TELECOM Digest OnLine - Sorted: Re: 10base-T & POTS in same Cat-5 cable?

Re: 10base-T & POTS in same Cat-5 cable?

David Clayton (
Thu, 28 Apr 2005 13:25:21 +1000

On Wed, 27 Apr 2005 12:35:45 -0500, GlowingBlueMist wrote:

> DaveC <> wrote in message

>> Is it acceptable to use 1 pair in a Cat-5 cable for POTS when 2 pair are
>> being used for 10base-T? Wondering about cross-talk, etc., introducing
>> noise between these two.

> No problem if you use 10base-T , usually none on 100base-T, but not
> compatible if you plan to use or upgrade to 1000base-T which some
> computers switches and routers are now supporting.

1000base-T uses all 4 pairs in a CAT-5 cable, so that's out -- and also
"beware" of certain switches that use the (previously) unused pairs
for externally powering Ethernet equipment.

I have only experienced problems with some digital PBX phones when
using a pair in a CAT-5 data cable running 10/100 Ethernet, analog
seemed to be ok even on long runs (50M+).


David Clayton, e-mail:
Melbourne, Victoria, Australia.
(Remove the "XYZ." to reply)

Knowledge is a measure of how many answers you have, intelligence is a
measure of how many questions you have.

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