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The UKHA-ARCHIVE IS CEASING OPERATIONS 31 DEC 2024


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Re: 2 questions...



Keith Doxey wrote:

> That shouldnt happen.
> You must use all 4 pairs for the 2 lines.
> DO NOT USE A SPLIT PAIR FOR THE THIRD WIRE OF EACH LINE
> That is the wire that carries the ringing circuit and if you use a
both
> wires of the pair one for each bell wire you WILL get overhearing as
you
> have created a long transformer winding which effectively puts them in
> contact with each other.

What you describe is the exact reason that phone wiring in NZ is no
longer done with a third wire.

The 3rd wire acts as an antenna for RF noise, and on cat 5 it is not
twisted with the balanced pair. The decoupling cap in the master socket
provides a nice path onto one line of the pair.

You are much better off using RJ45 connectors and getting a PABX adaptor
for any gear that has a requirement for the 3rd wire.

> Normal house telephone cable has 3 pairs and when people have a second
line
> the 3 unused wires are often pressed into service and you get exactly
the
> problem you have described.

I was under the impression that it was simply 6 wires all twisted
together rather then 3 actual pairs.

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