How to Test Phone Wiring

Phone signals and power coming from the telephone company runs into your house and ends up in the network interface device or NID mounted on a wall just outside your home. Your household telephone wires originate from the NID and are distributed around your house, terminating at telephone jacks. Telephone lines tend to bog down once in a while. When they do, you naturally wonder whether the problem lies in your household wiring or with the telephone company's equipment. There are ways you can pinpoint the problem the next time it happens.

• 1

  Get a working telephone and open the network interface device. Unplug the modular connector inside from its jack and plug the working phone into the jack. Listen for a dial tone, and call the telephone company from a working phone if you don't hear one. No dial tone means power and signals aren't coming from the phone company, and the phone company is responsible for any problem with the NID or the phone line beyond. It also means your house wiring is fine.

• 2

  Unplug any other devices that you have connected to the telephone lines such as security gadgets, caller ID, fax machines and modems and listen for a dial tone. If you hear a dial tone, one of the devices has caused the problem. To find the culprit, plug in each device one at a time and listen for a dial tone after doing so. If the dial tone stops after a device is plugged in, that device is dysfunctional and is the cause of your problem.

• 3

  Unplug all your telephone sets and test them one by one. Plug each phone into the test jack inside the NID and check if each one gets a dial tone. Some dysfunctional phones have a tendency to affect the whole circuit, which is why it is important to eliminate your phone sets from the list of suspected items. Replace any phone set that is dysfunctional.

• 4

  Go to the telephone hub if you have one. A phone hub is directly connected to the NID and distributes phone wires around your house. Plug a working phone into its test jack and listen for a dial tone. Plugging a working phone into its test jack will let you confirm that there is power running from the NID to the hub.

• 5

  Go to each phone and determine which phones do not have a dial tone. If you already know power is coming from the NID and from the NID to the phone hub (if you have one), and you know the telephone set at the end of the line is working, the absence of a dial tone suggests a problem in the telephone cable from the hub or NID up to the jack. Try to trace the line and find the junction where the problem lies.