Depending on whom you ask, the telephone is one of the world's greatest or worst inventions. Most people, however, agree that it is both. It can bring you the friendly voice of a loved one or that of a rude stranger at 2 a.m. It can deliver useful Web pages or annoying faxes. Sometimes you wish it would break--of course, then you would have to fix it!

How Does It Work?

A telephone is a low voltage transmitter and receiver for distributing and reproducing sounds over a distance. A call from a fixed telephone goes through a series of local and main exchanges that route it to the called telephone. The call may be transmitted over metal cables, radio links, fiber-optic cables, or a combination of these components. All together, it's called a telephone system. A cellular (mobile) portable telephone (see the Cellular Telephone Fix-It Guide) connects by radio signals to a nearby base station, then through telephone lines.

What Can Go Wrong?

The telephone itself may be defective. The modular jack may be defective. The phone lines inside the house, which are your responsibility, may be defective; the lines outside the house, which are the telephone company's responsibility, may be defective.

Fix-It Tip

Check your telephone bill. You may or may not be paying a small monthly charge for wiring service. If so, the telephone company will service all wires in your home's telephone system including those inside the walls and to the jack. If you're not paying for this service the company's not responsible for inside wiring.

How Can I Identify the Problem?

First, determine if the problem is with an individual telephone or the telephone line. If a phone does not operate at all, unplug it and plug another phone into the jack. If the second phone works, the problem is probably in the first telephone. If the second phone doesn't work either, plug the first phone directly into the telephone network interface module located outside in the box where the telephone lines enter your home. (If the box where the phone lines enter your home does not have a plug for the telephone, use the phone jack nearest where the lines come into the house). If the phone now works, the problem is inside the house. If the phone still does not work, the problem is in the telephone company's lines coming to the house. Contact your phone company for repairs.

Wiring a modular telephone jack.

If the phone does work when plugged into the telephone network interface module, the problem is between there and the module in the house. Use a screwdriver to remove the covers of both the network interface module and the modular jack, and disconnect the red and green wires. Telephone lines come with an extra pair of yellow and black wires, so substitute yellow for red and black for green at the telephone network interface module and at the modular jack. (If you have a second phone number for your house the yellow and black lines may already be in use.)

If you get a continuous dial tone, even when dialing, the red and green wires are probably reversed. Try the following options. If you have the same problem on all your telephones, remove the network interface module cover and switch the red and green wires leading to the phones. If the problem affects only one telephone, use a screwdriver to remove the cover of the modular jack serving that telephone and reverse the red and green wires leading from the jack to the telephone.

Other problems may occur within the telephone itself. Although many telephones can be replaced inexpensively, some problems can be resolved easily by checking connections and settings.

If there is no sound from a classic telephone headset, you may be able to remedy the problem (see below). Electronic phones are harder to service (sometimes impossible because many new ones are sealed).

What Parts, Materials, and Tools Do I Need?

Replacement parts are available at electronic and telephone supply stores and larger hardware stores. The tools you will need to fix a home telephone system include these:

• Telephone line tester
• Screwdrivers
• Denatured alcohol
• Emery cloth

Fix-It Tip

If you have many problems with your telephone service, consider purchasing a telephone line tester through an electronic supply store. With it you can easily test the telephone signal at the phone box outside of your house as well as individual lines and jacks within it.

What Are the Steps to Fixing It?

Improve transmitter sound on a standard phone:

1. Unscrew the mouthpiece cover and lift out the transmitter.
2. Clean off dirt with a foam swab dipped in denatured alcohol.
3. Clean metal contacts beneath the transmitter.
4. Raise the metal contacts slightly with a screwdriver and clean with an emery cloth.
5. Reassemble the headset and make a call. If poor sound persists, have the phone serviced by a professional or replace it.

Improve receiver sound on a standard phone:

1. Unscrew the earpiece cover and lift out the receiver.
2. Loosen terminal screws and remove the wire leads.
3. Clean the leads and screws with an emery cloth.
4. Reconnect each wire terminal securely to its screw.
5. Reassemble the handset. If poor sound persists, have the phone serviced by a professional or replace it.