How to Install a Phone Jack

Telephone jacks can be either flush or surface mounted, so be sure to buy a replacement jack that fits your particular setup.

flush and surface mounuted phone jacks

While phone lines are low in voltage, they carry enough current when they ring to give a mild shock, so it’s a good idea to disconnect the line before working on it. Also, never work on a phone line during a thunderstorm, since lightning can travel down the wire causing serious injury.

To disconnect the line, find the telephone interface box which is usually mounted on an outside wall where the phone lines runs into your house.

telephone interface box

Open the customer access panel and unplug the test jack.

removing wires from phone box

On older interface boxes without a test jack, unscrew the terminals and detach the wires, remembering which one went on which terminal.

older phone wire box

If the interface box isn’t easily accessible, take another phone on the same line off the hook to prevent it from ringing while working on it.

After checking to be sure the line you’re working on has no dial tone, unplug the phone from the jack. Remove the jack from the wall, noting which colored wires are hooked up to the terminals so you can match them to the new one.

removing phone jack from wall

While only two wires are required for a phone to work, the cable usually contains four or more to provide for additional lines or in case one line should fail. These are color coded with red and green normally used for the first line, yellow and black for the second, and blue and white for the third.

red green yellow and black phone wires

After removing the wires from the old jack, attach them to the new one. If the stripped ends of the wires appear discolored or brittle, cut off the damaged section and strip the outer insulation around the line back a couple of inches, being careful not to nick the wires.

stripping phone wire

Using a utility knife, cut back ½” to ¾” of the insulation around each wire.

trimming phone wire insulation

Bend the exposed end of the wire into a “U” shape with needle nosed pliers.

bending phone wire with pliers

Slip the wire over the corresponding terminal on the new jack so it wraps around the terminal in a clockwise direction.

slipping phone wire on terminal

After tightening the terminal screws, attach the jack to the wall, reconnect the line at the interface box, and plug the phone back in.

For more information about working on phone lines, check out our articles on: