Single BT Wall Master Socket & Back Box- IDC Terminals - 3/1AQuantity x 1Used for - This BT master socket should be connected to the main incoming telephone line into a property, it cannot be used as an extension socket. The faceplate is supplied with a standard single back box & fixing screws.How to fit - The BT drop cable coming from outside the property usually has orange, white, green and black wires. Usually (but not always) the orange and white internal wires are the active pair and go to connections 2 and 5 on the master socket, in some master sockets these connections are marked A & B. If you are removing or changing your current master socket, you can check which wires are the active pair by looking at the original wiring. Which way round the internal wires are connected does not usually matter, however the polarity can sometimes stop some equipment from working. One of the cables will have a voltage of -48V and this needs to go to pin 5 (B) and the other will have a voltage of 0V and this needs to go to pin 2 (A). Voltage can be checked by using a multimeter, if you do not have one, they are available in our shop. Connection of the active pairs into this master socket can be done using an IDC tool - a small scale technician’s tool for guiding wires into small sockets. If you do not have one of these, we have them in our online shop. The BT drop cable has more than 1 pair of internal cables therefore, this is for if you wish to have 2 or more lines in your property, or if a pair fails, the chances are that there are still existing pairs available, hence there would be no need to replace the drop cable. Fitting an extension - If you wish to wire an extension off this master socket, normally you would need to attach a double adapter into the front of it so it can still be used locally and so a cable can be run to your extension socket. If you would like a neater installation where the wiring can be done at the back of the faceplate, you would.