A couple years ago our phone jacks in the 2nd story quit working. We didn't fix them, just bought a multiple phone system. Suddenly our main phone jack in the kitchen has failed to work. The rest of the phones and phone jacks in the house are still working properly. How can I tell which wires are to be connected to what? The other jacks are not easily accessible or I'd try comparing to one of them. Thanks.

The Jack is officially referred to as an RJ-11 jack. It has 6 contacts. 1 and 6 are not used and should be empty. 2 through 5 are "used". 3 and 4 are used for line 1 (normally Red and Green). 2 and 5 are used for line 2 (normally black and yellow). If you only have 1 line coming into your house then only the center 2 wires are used (3 and 4 or red and green).

Casey

Just to add to Casey's answer. On all phone jacks and cables I have worked with, they are color coded. So all you need do is match the colors from the cable to the colors on the jack's terminals.

You also need to test the connection at the junction box.