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How to wire a BT telephone socket

Updated February 21, 2017

The choice to wire a British Telephones telephone socket typically arises from the need to install a telephone extension in your home. The incoming BT wire terminates at the master socket and all contemporary BT master sockets have a user panel that you can use to wire in extension cabling. It is important to know how to wire the user section of the BT telephone master socket using the correct procedure because the wiring you perform and any resulting consequences become your liability rather than the responsibility of BT.

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  1. Measure the distance between the BT master socket and the position where you want to install a telephone extension socket, using a tape measure. Take into consideration the route for the cable so that the extension wire does not trail across flooring and present a hazard. Allow an extra 15 cm (6 inches) of extension cabling at the site of both the BT master socket and the extension socket for wiring into the sockets.

  2. Obtain a hard-wired telephone extension kit that contains your required cable length as measured in the previous step. Use a utility knife to remove the thin plastic marked at the side or base of the extension socket back-box to create the point of entry for your cable. Fasten the extension socket back box to the wall with the supplied screws and according to the kit manufacturer’s instructions. Ensure you check that no pipes or wiring are behind the wall before installing the extension socket.

  3. Unroll the telephone extension cable. Push about 15 cm (6 inches) of one end of the cable through the back box entry hole you made in Step 2. Fasten the supplied cable clips over the extension cable at 30 cm (1 foot) intervals along your chosen route to the BT master socket.

  4. Use a utility knife to slice into the outer layer of the extension cable to about 2 cm (7/8 inch) along from the cable end in the back box to expose the plastic string that helps with stripping the cable insulation without damage to the interior wires. Grip the plastic string with your fingers or use tapered pliers and pull the string to expose between 4 cm and 5 cm (15/8 and 2 inches) of internal wiring. Trim the excess outer layer of insulation from the cable using a utility knife.

  5. Fasten the cable to the inside of the extension socket face plate, using the supplied cable tie that you typically find located in a small plastic bag that comes with the fixing screws. Separate the wires for easy installation into the six terminals on the face plate.

  6. Install the green wire with white rings into terminal one. Connect the blue wire with white rings to terminal two. Install the orange wire with white rings to terminal three.

  7. Connect the white wire with orange rings to terminal four. Install the white wire with blue rings to terminal five. Connect the white wire with green rings to terminal six. Fasten the face plate to the back box.

  8. Remove the user panel on the lower section of the BT master socket. Thread and fasten the cable through the cable entry hole on the master socket back box. Use the same cable stripping procedure as you did previously with the extension socket.

  9. Connect each wire to the respective terminal on the user portion of the master socket using the same colour coding as you did for the extension socket. Check you have the green wire with white rings at terminal one, the blue wire with white rings at terminal two, the orange wire with white rings at terminal three, the white wire with orange rings at terminal four, the white wire with blue rings at terminal five and the white wire with green rings at terminal six. Fasten the user panel back onto the BT master socket.

  10. Tip

    Use the supplied Insulation Displacement Connector tool to install wires on an IDC socket. Loosen the terminal screws and thread stripped wire into the terminals on a non-IDC socket, before re-tightening the screws to make the connection secure.


    If the BT master socket does not have a user panel located on the lower portion of the box, stop work and contact BT for advice in case BT needs to replace the master socket with an up-to-date version.

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Things You'll Need

  • Tape measure
  • Hard-wired telephone extension kit
  • Utility knife
  • Tapered pliers (optional)

About the Author

Residing in the coastal county of Devon, England, Jane Humphries has been writing since 2004. Writing for "British Mensa" nationally and regionally, Humphries has also held key roles within the High IQ Society. She received a Bachelor of Science, honors, in psychology with combined studies covering biology, statistics, economics, politics and sociology.

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