TSGL: Computer and Phone on CAT5 cable.

[Geoff Glave]

>If I remove any two pairs off the cat5 and use for the phone and the
>remaining six pairs are used for the PC done on both ends, will it
>work for both the pc and phone.

I did this once and it worked fine.

Not sure where you are, but here in North America the phone line only needs 
two wires, called the 'tip' and 'ring.'  If you look at an RJ-11 modular 
phone connector these are the two middle connectors, which are typically 
green ('tip') and red ('ring').

Inexpensive phone cables from handsets to the wall are typically only two 
wires, because that's all you need.

[The two wires on the two outside edges of the connector are typically black 
and yellow.  These are usually unused, or if they are used they're used to 
carry power to old phone systems (very rare), or are used for a second phone 
line.]

Your Ethernet Cat 5 cable will have four twisted pairs in it, for a total of 
eight wires.  Typically they are coloured like this:

Wire pair #1:
White/Blue
Blue

Wire pair #2:
White/Orange
Orange

Wire pair #3:
White/Green
Green

Wire pair #4:
White/Brown
Brown

However, Ethernet only needs two pairs, so you have two pairs left over.  
Typically, only pair #2 (white/orange, orange) and pair#3 (white/green, 
green) are used for ethernet, leaving pair #1 (white/blue, blue) and pair #4 
(white/brown, brown) unused.

In my case, I used one of these remaining pairs (i.e. two wires) for my 
phone.  If memory serves I used pair #4 (white/brown, brown).

At each end I simply attached an RJ-45 Cat 5 jack to pairs 2 & 3 and 
connected an RJ-11 phone jack to pair 4.  I left pair 1 'loose' in case I 
wanted to use them for something else later.

If memory serves, it worked fine.  There might have been some data 
degradation, but if there was I never noticed it.

Cheers,
Geoff Glave
Vancouver, Canada