Doing your own telephone wiring Four-strand wire supports up to two phone lines. If you are installing three or four lines, you might also consider buying eight-strand wire. The color coding conventions for this kind of wire are as follows: (There's also six-strand wire, which is the same as eight-strand wire with the brown pair left out. TELEPHONE SOCKET WIRING - HOW TO DO IT House telephone wiring uses cable containing six 0 diameter solid conductors. It is important that this size of wire is used or a good electrical connection cannot be guaranteed and there could be problems in the future with the system. Never use stranded wire, mains cable or bell wire. Telephone Wiring Colour Code - BT Telephone Extension Telephone Wiring Colour Code & BT Telephone Extension Socket phone cable connection details. How to wire a BT socket with pictures - free DIY help & advice. Telephone Extension Socket Telephone Extension Socket wiring colour code, DIY advice. Click here for Telephone Connection colour codes and description of what the wires do. Telephone Wiring Connections | DoItYourself Whether you're wiring connections for telephones in a new house that is under construction, or whether you are installing new telephone wiring in an existing residence, you'll need to know something about telephone wiring jacks and the wiring you connect to those jacks.