How to Connect a Phone Line to an RJ45

Written by alice godfrey
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The modular plug at the end of a telephone cable is called an RJ45. The plug has a series of contacts that connect to a telephone cord so that a telephone's cable can be plugged into a modular socket on a telephone connection (i.e., a telephone wall plate). You can connect the end of a landline telephone cable to an RJ45 plug to make it compatible with a modular socket. You will need to know how to solder in order to complete this task.

Skill level:

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Things you need

  • Landline telephone
  • Utility knife
  • Ruler
  • Wire stripper
  • Soldering iron
  • Solder
  • Electrical tape

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  1. 1

    Snap the two sections of the RJ45 plug apart with your fingers. Place the section that has the slots on a work surface. Rotate the section so that the slots are on the bottom, closest to you.

  2. 2

    With a utility knife, cut four inches in through the outer insulation at the end of the telephone cord. Peel the insulation apart to get to the wires inside. Pull the wires out from inside the insulation.

  3. 3

    With a wire stripper, strip one half inch of insulation from the ends of the red, green, white and black wires. Twist the exposed end of each wire between your fingers to form a smooth rod.

  4. 4

    Heat up a soldering iron for six minutes. Apply a drop of solder to the end of each wire. Let the solder cool for two minutes.

  5. 5

    Insert the end of the white wire with green stripe into the leftmost slot on the RJ45 section that is on the table. Hold the tip of the soldering iron against the exposed wire for two seconds. Let the solder cool for 30 seconds.

  6. 6

    Repeat this soldering procedure with the white wire with orange stripe, and insert it into the slot next to the leftmost one. Then solder the blue wire with white stripe into the slot next to the white wire with orange stripe.

  7. 7

    Repeat the soldering procedure with the white wire with blue stripe and the next open slot from the left, followed by the orange wire with white stripe and the next open slot from the left. Repeat the procedure with the green wire with white stripe and the next open slot from the left.

  8. 8

    Unplug the soldering iron so it can cool off. Snap the two sections of the RJ45 plug back together. Wrap strips of electrical tape around the exposed outer cable.

  9. 9

    Hold the RJ45 plug with the tab on the bottom. Insert the RJ45 plug into the modular socket on the telephone wall plate. Wiggle the plug gently to engage the tab in the socket; you might hear a click to signify that this has happened. The landline telephone can now be used to place calls.

Tips and warnings

  • You should wear protective gloves when handling a heated soldering iron to prevent burns.

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