How to Wire a Telephone Jack

  • 01 of 06

    Telephone Wiring Basics

    Young woman screwing phone jack into wall, side view
    Bruce Laurance/Digital Vision/Getty Images

    Old phone cable typically has four wires inside: red, green, black and yellow. If you're extending a line to a room or other part of the house, you can use this type of cable, or you can use newer Category 3 or 5 (Cat-3 or Cat-5) data cable, which also has multiple wires but with a different color scheme. Category cable works just as well as the old cable for phone service, and it works much better for data (such as for a DSL internet connection). The steps below show you how to install a new phone jack and make sense of the color combinations. 

    Note: Telephone wires inside your home carry a very low-voltage electrical current and are safe to work on without shutting off the power. In fact, only the phone company can shut off the power to the phone system. But just to be safe, don't work on phone wiring with wet hands or when standing in water. 

    This project assumes you have already run the appropriate phone cable through walls to the location of the new phone jack. 

    Tools and Supplies You Will Need

    Tip: There are several types of telephone wall jacks you can buy, depending on where you'll be installing the jack. Baseboard jacks are square-bodied fittings that screw onto the face of baseboard moldings. For mounting on walls, use a wall-mount that sit on the face of the wall; with this style, you plug the phone cord into the jack. So-called flush-mount jacks are designed if the body of the phone, rather than a cord, is attached directly to the jack.

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  • 02 of 06

    Strip the Outer Sheathing

    Strip 2 to 3 inches of the outer sheathing from the phone cable, using wire strippers. An old-style four-wire cable fits the 10-gauge slot on the wire strippers. Rotate the strippers as needed to cut all the way around the sheathing, being careful not to cut into the insulated wires inside the cable. Once the sheathing is cut all the way around, the piece can be pulled free from the cable, exposing the inner wires. 

    Alternatively, some phone cables have a pull cord inside that strips the sheathing as you pull back on it. In this case, start by stripping only a small amount of the sheathing using wire strippers, then use the pull cord to cut back the sheathing 2 to 3 inches. Trim off the portion of cut sheathing. 

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  • 03 of 06

    Untwist the Individual Cable Wires

    Untwist the individual cable wires from one another. Strip 1/2 to 3/4 inch of insulation from each wire that you need, using the 20- or 22-gauge slot on the wire strippers. In many cases, you'll need to strip only two of the wires if you are installing a standard one-line residential phone line. A second pair of wires is used if you are installing a second line, such as a fax line or second voice-phone line. 

    Old four-wire cable:

    • Line 1 (primary phone line): red and green
    • Line 2 (secondary line): black and yellow

    Cat-3 or cat-5 cable: 

    • Line 1 (primary phone line): blue and white-with-blue-stripe 
    • Line 2 (secondary line): orange and white-with-orange-stripe
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  • 04 of 06

    Mounting the Plate

    Remove the cover from the front of the phone jack, exposing the mounting plate and mounting screw holes. If the phone cable is run inside the wall, thread it through the opening in the plate as you position the plate against the wall over the access hole. If the phone cable is surface-mounted, such as if it is being run along the floor line of the baseboard, then it is typically inserted through a notch in the side of the phone jack. 

    Mount the plate to the wall, molding, or other structure, using a screwdriver and small wood screws or drywall screws. Some phone jacks may have self-adhesive strips for securing the plate to the wall, but if this type of jack also has screw openings, it is a good idea to reinforce the installation with screws. 

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  • 05 of 06

    Connect the Wires

    Connect the stripped wires from the phone cable to the corresponding screw terminals on the jack, using the following color combinations (each jack terminal is identified by the color of the wire that is preattached to it):

    Old four-wire cable: 

    • Line 1 (primary phone line): red wire to red terminal; green wire to green terminal
    • Line 2 (secondary line): black wire to black terminal; yellow wire to yellow terminal

    Cat-3 or cat-5 cable: 

    • Line 1 (primary phone line): blue wire to red terminal; white-with-blue-stripe wire to green terminal
    • Line 2 (secondary line): orange wire to yellow terminal; white-with-orange-stripe wire to black terminal 

    To make the wire connections, loosen each terminal screw with a screwdriver. Wrap the bare copper end of the wire around the screw in a clockwise direction, using needle-nose pliers. Tighten the screw to secure the wire. The wire insulation should just touch the screw terminal and there should be no excess bare wire extending out from the screw. 

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  • 06 of 06

    Reinstall the Cover

    Reinstall the cover on to the jack's mounting place. Some covers are secured with a screw; others simply snap into place. Plug a phone into the jack to make sure the line is working properly.