How to check for problems in a house phone line

Written by kenneth w. michael wills
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How to check for problems in a house phone line
No dial tone? There are ways to troubleshoot the problem. (telephone 4 image by Aussiebloke from

Difficulties with the phone lines at your residence usually distinguish themselves easily. The troubleshooting process should focus on three possible causes: 1) a defective handset or cordless phone base, 2) external wiring or D-mark problems or 3) internal wiring or jack problems. Two common problems, a defective phone (which may need a replacement handset or base) and D-mark or external wiring (usually corrected by contacting your telephone company), are simple to fix. The challenge, however, is troubleshooting to find the problem, and fixing an internal wiring or jack problem.

Skill level:

Things you need

  • Flathead screwdriver
  • 2 corded analogue test phones
  • Tone generator
  • Induction amplifier
  • Gloves

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  1. 1

    Unplug all communication equipment from all telephone jacks in the home.

  2. 2

    Wait for about 10 minutes and then proceed with troubleshooting.

  3. 3

    Plug a corded analogue test phone into each individual telephone jack. Listen for a dial tone or static. Repeat the procedure with a second corded analogue test phone to ensure that the first telephone is not the origin of the problem.

  4. 4

    Determine whether the trouble occurs only in certain jacks or in all phone jacks. If the occurrence is isolated to one or two jacks, faulty wiring or jacks inside the home are the likely culprits. If the trouble occurs in all of them, you will need to conduct testing at the D-mark (short for telephone network interface device), which is located outside. If you're in an apartment, it may be located in the basement or inside the apartment itself.

  5. 5

    Proceed to the D-mark to continue with your troubleshooting. The D-mark is usually recognisable by your telephone company logo or is labelled "network device."

  6. 6

    Use the flathead screwdriver to remove the cover from the D-mark on the customer access side.

  7. 7

    Take out the plug from each jack in the network interface device. Plug in one of the corded analogue test phones. Listen for a dial tone and then proceed to conduct a test call. If a dial tone is present and the call connects just fine, the problem is with the wiring or jacks inside your residence.

    On the other hand, if you do not hear a dial tone or if there is static on the line, the problems is with the outside wiring. Confirm the results of your test by repeating with the second corded analogue test phone. Be sure to conduct this test for all jacks with telephone numbers into your home.

  8. 8

    Insert all plugs back into the jacks, close the cover on the network interface device and screw it back in place. Head back inside to continue troubleshooting.

  9. 9

    Remove the jack cover from any jacks that did not work in Step 3 with your test phone plugged in, and study the jack's connection terminals. Try to wiggle each individual wire to get a dial tone. Be sure to wear gloves while conducting this procedure to prevent the possibility of a mild electric shock. If you do not get a dial tone, the jack might not be the problem. Continue with the last step.

  10. 10

    Unplug your test phone from the jack and plug your tone generator in its place. Insert the tip of the amplifier into the opening of the phone jack. Listen for the generator tone from the amplifier. If you do not hear a tone, this indicates a severed wire or, possibly, some loose terminals. Repeat this process with all jacks in your residence until you've located your problem.

Tips and warnings

  • It is best to conduct this testing to isolate your problems before contacting the phone company. Usually the phone company will tell you the problem is with the wiring in the home, unless you can confirm otherwise.
  • Do not attempt troubleshooting during a thunderstorm, as a lightning strike could send a current of electricity rushing through the phone lines and deliver a major shock.

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