Question : Can I run two phone lines through a single CAT6 cable?
I want to run two phone lines upstairs to my office, which will be a 30m run. As CAT5/6 cable is four twisted pairs, can I run both phone lines through it? I intend to use one for voice+DSL, and the other for fax.
cat6 cable

Best answer:

Answer by GTB
yes

In the “good old days” there was a 4 wire conductor – black, red, green, and yellow. Phone line 1 uses only red and green on pins 2 and 3 of a 4 pin RJ11 jack. Phone line 2 uses black and yellow on pins 1 and 4. If you had only 1 phone line, black and yellow were not used.

Now let’s go to a CAT5 line which uses RJ 45 jacks. You have 4 pairs. For 2 phone lines, you use only 2 pairs.

Most commonly people use this color logic pin 1 – orange white, pin2 orange, pin3 green white, pin 4 blue, pin 5 blue white, pin 6 green, pin 7 brown white, pin 8 brown.

Now for an RJ 45 socket to work with an RJ 11 phone style plug, you use only pins3, 4, 5, and 6 of the RJ 45 with pin 3 equivalent to RJ 11 pin 1, pin 4 of RJ 45 equivalent to RJ pin 2, pin 5 of RJ 45 equivalent to pin 3 of RJ11 and pin 6 of RJ 45 equivalent to pin 4 of RJ 11. RJ 45 pins 1, 2, 7, and 8 are idle.