I have 2 phones lines (cira 1955)that come in separately on a 3 wire(all black) twisted cable, only using 2 wires, to the interface, and then on to a jack, again using 2 of the 3 wires of the same type of cable, rather than the more common 4 wire cable consisting of red, green, yellow and black. Can this 3 wire cable support 2 lines, using one of the wires as a common for the 2 lines, in order to bring the 2 lines to an existing jack location? Thank You

No - if I understand you correctly you already have two 3-wire cables to the NID - one for each line - and you then want to combine the two active pairs onto one 3-wire internal cable run to a 2-line jack? I think this could mess up the signaling on your line - it is true that one of the leads of each pair is considered a "ground," but if you bridge two of these togther on two different lines there may be enough of a voltage difference to cause current flow, which would most likely manifest itself as noise on the line. Also, the current flowing back to telco on the ground leads of each line would be unbalanced with the current flowing out, which could cause problems with how the telco equipment functions, particularly when both phone lines are off hook.

To add to ebaines info. 2 conductors are needed for each line, neither can go to ground or connect to each other. You can have line 1 on one jack and line 2 on other jack, may not be a problem if 1 is a Fax.

Hi
Thank all you for best answers
I will done it too
May I problem with it?

No.