How to Install an Extra Phone Jack

Even though cordless phones are so common nowadays, it's often still useful to put in another phone jack. If you need a wired phone in a different room, have remodeled your kitchen, or even want to move your DSL router upstairs, you can pay the phone company a lot of money, or spend a few hours one afternoon and do it yourself. It's really very easy. This tutorial only presupposes a basic understanding of how electrical circuits works.


If your other phones are still working (all of them for a home run, or the one at the jack you tapped from), check your new jack’s wiring.

Use the documentation to make sure you’ve attached your two wires to the right terminals. You may be able to unscrew the wires and hold them against different terminals with the phone off-hook to see if you hear a dial tone.

Get a multimeter and test the wire.

You’re looking for voltage between the two wires you’ve been using, which should be about 48 volts DC.

If all else fails, check the wire itself – you want to check for continuity between at least the pair of wires you’re using, and the same colors on the opposite end.

If you give up, call your phone company or an electrician.


  • Check with your wife before running wire along the baseboard.
  • You can use any pair of wires you want, but blue/white and white/blue are the standards, and you’ll make anyone else who works on your line crazy if you use anything different.
  • Polarity shouldn’t matter.


  • The electricity on this line is pretty safe. When a phone is on-hook, no electricity flows. When a phone is off-hook, about 48V DC flows – safe enough to touch. But when the phone rings, the voltage changes to 90V AC, which is pretty close to what you have in a normal power outlet. If you’re concerned by this, disconnect your phone line at the demarcation point while you’re doing the wiring. If you open up the box outside, you should find a plug with a short phone cord. Unplug that and you’ll be set.

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