Adding a Jack to an Existing Phone Line

When you buy a new phone, answering machine, caller-id device, modem, or fax machine you need a phone jack to plug it into the phone line.  With the ever increasing demand for access to dial tone, it seems there are never enough phone jacks.  Adding a jack on your existing phone line is a fairly simple process.  The advice below should help!

If you think you may be adding an additional line in the future, take a few moments to look at the pages on wiring for a second line.  You may want to do the wiring for your additional jack a little different if you think you might add another line later.

Two wires (one "pair") are needed for most phone line connections.  Normal station cable (what your phone tech may call "JK") used for residential installations has four wires (two "pair").  Single line installations only use one pair, but you should wire both pairs at your new jack.  If your home was originally wired with both pairs connected to all of the jacks and you maintain this practice, then your home will be essentially "two-line ready".

In the following advice, I have referred to the wires by color.  If your cable has more than two pairs, the colors will be different.  See my page on Wire Color Codes to translate the colors of your multiple pair cable.

Step by Step Advice for Wiring for Adding a Jack

Step 1 - Check in the customer side of the NID.  Ensure that the green and red pair of your cable is attached to the screw posts.  If you find that your black and yellow pair is in use, the green and red pair of your cable may be defective.  You will have to adjust your connections accordingly.

Step 2 - Examine the routing of your phone cable to determine the best location to tap into your phone line.  Determine where all junctions and jacks are located.  If you find junctions, ensure that all wires of the same color are connected together.  Jacks may also be a junction location.  Most people will be able to add a jack to their existing line by simply connecting a cable from an existing jack to the new jack.  However, if your existing cable is in a pure "star topology" you should run a new cable to the central hub if reasonably possible.  Understandably, sometimes this is more trouble and is not warranted.  If you are relatively sure that you will never need the benefits of "star topology', then simply identify the existing jack that is physically the closest to the location where you wish to place the new jack.  The closest jack may not be in the same room.  An existing jack in adjacent room on a shared wall between the rooms is an ideal choice.  The availability of a path to route the cable is your primary concern.  If at all possible you want to route your cable within the walls and ceiling.  This protects the cable and does not detract from the appearance of your home.  If you must route cable outside the walls and ceiling, choose a path that is relatively out of sight and secure the cable so that it does not be come a safety hazard and is not subject to being damaged and becoming a potential point of failure.

Step 3 - Install cable from that location to the new jack location.  This may involve a little carpentry or drywall work.  I will not go into the detail of that process.  If you need help with these items, please get professional assistance or consult a "Do-It-Yourself" book.

Step 4 - Connect the wires to the new jack as shown in the diagram at the left.  The terminals of the jack should be marked to indicate the color of the wire to attach to each screw post.  Connect the wires at the other end of the cable to your phone line.  If you use an existing jack to make this connection, it is done as shown in the diagram at the right.  If you connect at a junction, simply connect the new wires to the terminals with wires of matching colors.

Step 5 - Test your work.  Plug a phone into your new jack and ensure that it works properly.  Also test all the other jacks to ensure that your work has not resulted in a broken wire and caused one of your existing connections to fail.

Enjoy your expanded phone service!

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