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How to Add a Phone Line

A step-by-step guide to installing a second phone line for voice, fax, or e-mail

Imagine the convenience of having a second telephone line in your home. Not just an extension to your current phone, but another line with its own number. It could be used as the kids' phone or reserved for home business or Internet use. And all the while your original phone line will remain open for making and receiving calls.

Installing a new phone line is surprisingly easy and safe. Phone wires carry a very weak electrical charge and you'll only need a few basic tools to complete the job. But best of all, most of the wiring needed to connect a second phone line is already in your home. The telephone cable in your house right now contains at least four wires, but only two of them are connected to your current phone. Therefore, you can tap into the two unused wires to feed the new phone line.

Steps // How to Add a Phone Line
1 ×

Adding a Phone Line Overview

Step One // How to Add a Phone Line

Adding a Phone Line Overview

Adding a Phone Line
Illustration by Gregory Nemec

Adding a second telephone line to accommodate a dial-up modem, a fax machine, a new home business, or a chatty teenager can cost you as little as $60 or up­ward of $160. The difference is whether you have the phone company run the wires inside your house or do it yourself. This task is not difficult, requires only a few basic tools, and doesn't involve high-voltage electrical current.

Although it's best to run new wire from your network interface device (a junction box usually mounted on the outside of your home), when there isn't a clear pathway to the room where you want a new line, you can use the wiring already in place in your home. That's because all telephone cable contains at least four wires: red, green, black, and yellow. But only two of them - the red and green ones - are typically used to connect your primary phone. This leaves the black and yellow wires to power a second line.

To start, you need to contact the telephone company and request a second phone line. They'll assign a phone number and send out a technician to bring the new dial tone to the network interface for a $50 to $75 fee. (If you have an outdated interface, the telephone company will install a new one for free.) Tell them you'll be doing the inside wiring yourself.

For our project, we tapped into an existing phone jack that's set flush in the wall. We then connected the unused black and yellow wires from the cable that runs to this jack with two of the wires from a new length of quad-wire cable - sometimes called station wire - and ran it along the top of the baseboard, through the wall, and into an adjacent bedroom. There, we connected the new cable to a new, surface-mounted phone jack. Once you make a final connection at the network interface, you're ready to receive calls or dial out on your new line.

2 ×

Drill an Access Hole

Step Two // How to Add a Phone Line

Drill an Access Hole

adding a phone line
Photo by Matthew Benson

Even though phone wires carry very little electricity, play it safe and disconnect the line you're working on by taking the phone off the hook.

Unscrew the cover plate from the existing flush-mounted phone jack, but don't disconnect any wires.

Using a 1/2-inch-diameter spade bit and a cordless drill/driver, carefully bore a hole down through the bottom of the jack box.

Tip: Don't work on phone lines during an electrical storm.

3 ×

Run the Cable Behind the Drywall

Step Three // How to Add a Phone Line

Run the Cable Behind the Drywall

Running the cable behind the drywall
Photo by Matthew Benson

Bore a 3/8-inch-diameter hole through the wall directly below the jack and just above the baseboard.

Cut and straighten a wire clothes hanger with pliers, then bend a narrow hook on one end.

Feed a length of quad-wire telephone cable down through the hole in the jack box.

Push the hooked end of the wire through the hole in the wall, grab the cable, and pull it into the room.

4 ×

Staple the Phone Cable in Place

Step Four // How to Add a Phone Line

Staple the Phone Cable in Place

Stapling the phone cable in place
Photo by Matthew Benson

Run the cable along the baseboard to the point in the room where it will go through the wall.

Using a staple gun that has a cable-stapling nosepiece big enough to fit around the whole wire, attach the cable to the top of the baseboard, spacing the staples about 10 to 12 inches apart.

If the room has carpeting, you can hide the cable underneath, stapling the cable down alongside the wood tack strip.

5 ×

Drill a Hole into the Adjoining Room

Step Five // How to Add a Phone Line

Drill a Hole into the Adjoining Room

Drilling a hole into the adjoining room
Photo by Matthew Benson

Finish stapling the cable at a point on the wall that lines up with the spot in the adjoining room where the new jack will go.

Drill a 3/8-inch-diameter hole completely through the wall, just above the baseboard, with a 16-inch-long phone installer's bit.

Feed the straight end of the wire hanger through the wall.

Wrap the end of the quad-wire phone cable around the hanger's hook several times.

6 ×

Bring the Cable into the Room

Step Six // How to Add a Phone Line

Bring the Cable into the Room

Bringing the cable into the room
Photo by Matthew Benson

Walk around to the adjoining room and slowly pull the cable through the wall.

Staple the cable to the baseboard close to the wall and cut it off, leaving 4 inches protruding from the hole.

Carefully trim 1 inch of the outer sheathing from the cable, then strip 3/8 inch of insulation from the red and green wires. Don't strip the yellow and black wires.

7 ×

Install a Surface-Mounted Jack

Step Seven // How to Add a Phone Line

Install a Surface-Mounted Jack

Installing a surface-mounted jack
Photo by Matthew Benson

Attach a new, surface-mounted jack to the baseboard right next to where the cable protrudes from the wall. If the jack has an adhesive back, simply peel off the paper liner and stick it to the baseboard. If it's a screw-mounted jack, fasten the base plate to the baseboard with the screws provided.

Pry the cover off the jack using a screwdriver.

8 ×

Make the Connections

Step Eight // How to Add a Phone Line

Make the Connections

Making the connections
Photo by Matthew Benson

Connect the cable's red wire to the red screw terminal on the new jack. Don't connect the yellow or black wire.

Snap the cover plate onto the jack.

Now go back to the existing flush-mounted jack and find the unused (black and yellow) wires from the existing phone cable. Using wire connectors, join the yellow wire from the existing cable to the red wire of the new quad cable. Join the black wire to the new cable's green wire.

Replace the cover plate on the flush-mounted jack.

9 ×

Secure the Wires at the Interface

Step Nine // How to Add a Phone Line

Secure the Wires at the Interface

Securing the wires at the interface
Photo by Matthew Benson

Open the door of the network interface device on the outside of your home. Look for two small flaps labeled with the old and new phone numbers, or with Line 1 and Line 2. Open the flap marked Line 2 (or with the new phone number) to reveal two screw terminals.

Locate the cable that enters the interface from inside the house. Its yellow and black wires won't be connected.

Connect the yellow wire to the red screw terminal and the black wire to the green terminal.

Close the flap, then shut and latch the outer door.

Hang up the phone on Line 1, then plug a phone into the new surface-mounted jack to test your new number.


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