Telephone Wiring Colour Code

Telephone Wiring Colour Code BT NTE5 Master Socket

The following pictures show the standard BT Telephone Wiring Colour Code used with the BT NTE5 Master Socket. Please note you must use the correct inserter tool to push the wires in to the phone socket IDC connectors. Failing to do so will open the blades permanently damaging the connector. It will no longer hold the wires, with no option but to throw the socket away. Don’t strip the insulation from the wires when terminating the telephone cable. The blades are designed to bite through the insulation and make a connection.

For new sockets, spare parts and the correct inserter tool click here Sockets and Parts

Telephone Line cable coming in to property from the pole

NTE5This picture shows the external Dropwire cable from the telegraph pole or lead in wired directly to the rear of the BT Master Socket NTE5. Terminals are marked ‘A’ and ‘B’ and can be screw type terminals, or IDC inserter type as shown in the photo.



BT External Telephone Cable Colour Code

Normally, the first pair used for your telephone line is solid Orange, solid White. This applies to Underground fed properties with older BT cable, and BT overhead ‘Dropwire’.

A second telephone line with a different phone number would terminate on solid Black and solid Green.

BT external overhead cable contains 3 red, or 3 yellow wires. These should not be used as conductors. They are steel support wires to prevent the phone cable from sagging or stretching when suspended overhead. BEWARE when cutting or stripping this cable – the wires are EXTREMELY sharp and will leave a nasty prick or cut. Good wire cutters are essential when cutting BT Dropwire.This cable is heavy duty to cope with any kind of weather.

In the picture I have stripped back the cable, cut the steel support wires approx 1cm length, folded back and taped around. This protects your fingers from a painful spike when terminating. Do not underestimate the danger of the steel support wires. Follow my telephone wiring colour code and things should work first time for you.

Telephone Master Socket Wires

BT Master SocketThis is the Telephone Wiring Colour Code for the NTE5 BT Master Socket, with the cable feeding extension sockets attached to the customer removable front plate. You can see the Test Socket revealed to allow you to check the BT line before your own wiring.
NTE Front Plate


This is how the Telephone Wiring Colour Code looks wired with the stripey telephone cable. Note that this is the latest type available with a Bell Circuit Filter (the cylindrical protrusion next to the terminals)

Telephone Wiring Colour Code – What do the wires do?

Telephone Extension Sockets have 6 connections labelled 1 to 6. Only 3 connections should be used – connections 2, 3 and 5.
2 and 5 give you dial tone and allow you to make and receive calls. Terminal 3 is reserved for the Bell Circuit to link extension sockets to the Master Socket. Without it the other phones wouldn’t ring on an incoming call.

Increase Internet Speed

The change in this practise though came along with Broadband as the ADSL filter now has the component to enable each phone to ring. The Bell Circuit, pin 3, should therefore not be connected if you would like faster broadband. By removing this on all telephone extension sockets in your house you will almost certainly see increase internet speed instantly!

BT Stripey Telephone Wire Colour Code

telephone wiring colour codeThis picture shows a conventional telephone extension socket correctly wired with the stripey cable.




BT Solid Colour Telephone Wiring Colour Code

Extension Socket Colour CodeThis socket is connected to the latest solid colour coded BT internal cable (which oddly is the same colour code as very early BT cable). No need to terminate the brown wire. Always leave slack so that if you make a mistake you simply pull out the wires and re terminate. Any slack cable must be tucked inside the box before securing the front plate with screws.

Click here for Telephone Connection colour codes and description of what the wires do.

Images used on this website are subject to copyright and not permitted to be copied without written permission. Telephone Wiring Colour Code, Telephone Extension Socket and Telephone Master Socket NTE5 brought to you by Geoff Grove.