* First, disconnect the phone line in order to avoid any kind of electrical shocks or injury. To do this, locate the telephone interface box, which is normally placed outdoors.
* Now, unlock the customer access panel of the box and unplug the test jack inside.
* Some phone interface boxes do not have a test jack. In such cases, unscrew the terminals and remove the wires. Make sure to keep a track of which wire went on which terminal.
* Once the wires are detached, the phone should not have any dial tone. Check that the phone is dead and remove the phone from the jack.
* Now, remove the jack from the wall, remembering which colored wires are connected to the terminals. These color coded wires are generally red and green used for the first line, yellow and black for the second and blue and white for the third line.
* Once you remove these wires from the old jack, affix them to the new one. In case the stripped ends of the wires look weak or faded, cut off the damaged fragment.
* Next, tear up the outer insulation sheath around the line back for a few inches. Ensure that you do not cut or damage the wires, but only nick back ½” to ¾” of the insulation around each wire.
* With the help of pliers, twist the bare end of the wire into a “U” shape and slide the wire into the corresponding terminal on the new jack, noting that it coils around the terminal in a clockwise direction.
* Now, tighten the terminal screws and mount the jack onto the wall. After you are done with connecting back the line at the interface box, you are ready to plug the phone back to the new jack.