Can one use the unused wires in a network CAT 5 (and 5e, 6) cable for a
telephone connection?

And just which unused wires would they be?

Are you under the impression that they put extra wires in CAT5 just to have
something to do?

In article <eOr7tc9bFHA.***@TK2MSFTNGP12.phx.gbl>, "NoNoBadDog!"
<no_@spam_verizon.net> wrote:
Ethernet uses four wires (pins 1, 2, 3, and 6) to carry signals.  I
haven't tried it, but I think that using the other four wires for
telephone connection(s) will probably work OK.  It might give less
than optimal Ethernet performance because of crosstalk from the phone
wires to the signal-carrying wires.  Try it and see.  Be sure not to
untwist more than 1/2 inch of the signal-carrying wires.

Red,

Theoretically, yes, it's possible.  I've seen discussions in comp.dcom.cabling
about the 2 non-used pairs being used for voice communications.  Realising that
the 4 pairs of wires aren't connected to the RJ-45 plugs in a straight sequence
- ie pair 1 - pair 2 - pair 3 - pair 4, you can't just split the cable as run,
you have to terminate the cable with a standard RJ-45 connector, then split the
connections inside the jack that the RJ-45 connector plugs into.

But yes, some folks claim to have used a single Cat-5e (100mb) cable for both
data and voice when they wired their house.  Of course, a Gigabyte network won't
work that way, so splitting the cable will only work til you go to Gb speeds.

Yes, that was the intention.

Have you ever noticed that an RJ11 plug actually fits into an RJ45
connector?
Well, it does.

And telephony uses the centre 2 pins on the RJ11.
Plug the RJ11 into the RJ45, and the telephony is now
on the centre 2 pins of the RJ45 ( 4+5 )

Ever wondered why ethernet uses pins 1+2 one way, and 3+6 the other?
Seems odd pair splitting.

Well, there's the answer.
Because pins 4+5 were reserved as a pair for telephony.

I've never actually seen this in use ( telephony on 4+5, ethernet on 1+2,
3+6 ) but that was the original intention, so a single wiring system could
serve the phones and data.   It may not perform too well with 100Mbit
ethernet, due to crosstalk. I don't know, I've never tried.  I also think
gigabit ethernet perhaps requires all 4 pairs for data.

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