How to Wire Up a Telephone Extension

Written by raul avenir
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How to Wire Up a Telephone Extension
Additional phones can help make your home a better place to live. (telephone image by Alexander Babich from

Not having enough telephones inside your house can make you run from room to room every time your phone rings. You can avoid this situation by installing additional phones in your house. Telephone extensions can help prevent accidents, save you time, and allow you to enjoy phone conversations in more comfortable areas of your home. Learn how to install a telephone extension and improve the quality of life inside your home.

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Things you need

  • Screwdrivers
  • Wire stripper
  • Diagonal pliers
  • Cable staples
  • Telephone cable
  • RJ-11 surface mount jack

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  1. 1

    Open the telephone interface box or Network Interface Device NID outside your house. The NID is typically located on a wall nearest to where the telephone cable runs into your house. Unplug the modular connector found inside in order to disconnect the house line from the telephone company line and prevent low-voltage electric shock when you're working on the phone lines.

  2. 2

    Look for a telephone jack closest to the spot where you plan to install a new telephone. You will need to connect a phone cable from the existing jack (call this point A) up to the spot where you wish to place the new phone (call this point B).

  3. 3

    Map the route that you will take to run the telephone cable from point A to point B. You can run the cable along baseboards and inside ceilings, but do not place the cable alongside power lines to prevent interference. Choose a route that will be easy to install, but least visible. Measure the length of telephone cable that you will use following the route from point A to point B using a tape measure. Add 3 feet to your measurement to allow for slack and extra length.

  4. 4

    Get the telephone cable and strip off 3 inches from the outer cover to expose four inner wires coloured green, red, yellow, and black using a pair of diagonal pliers. Strip off 1/2-inch of insulation from each of these wires using a wire stripper. Perform the same procedure on the other end of the telephone cable

  5. 5

    Unscrew the cover or faceplate of the existing phone jack at point A and loosen the terminal screws inside using a slotted screwdriver. Wrap each colour-coded telephone wire clockwise around its matching colour-coded terminal screw on the jack. Tighten the terminal screws and screw the faceplate or jack cover onto the outlet box on the wall. Run the telephone cable along the route that you mapped earlier and fasten it along the way using cable staples. Do not pierce the telephone cable with staples.

  6. 6

    Get the RJ-11 surface mount jack that you will install at the new location (Point B), unscrew its cover, and loosen all the terminal screws inside using a screwdriver. Get the other end of the telephone cable and wrap each colour-coded telephone wire clockwise around its matching colour-coded terminal screw on the new jack. Tighten the all terminal screws with a screwdriver.

  7. 7

    Mount the new jack on the wall with a screw or double-sided mounting tape that came with the jack, and replace the jack's cover. Go outside your house, open the NID or telephone interface box, and replug the modular connector inside the NID to reconnect the main telephone line. Plug a telephone into the new jack and listen for a dial tone or place a call to test the connection.

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