How to Test a Phone Line: 8 Ways + Expert Tips

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A simple guide to diagnosing phone line service problems
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Problems with your phone line can be really irritating, but you can likely figure out what’s wrong. First, look for connectivity issues inside your home to see if that's your issue. If the problem remains, make sure your home is getting service from the outdoor phone lines by checking for a phone line fault. You might also use a multimeter or voltmeter to check for a phone signal or test for faults in your interior wiring. This wikiHow article teaches you how to check your phone line, with expert tips from electrician Ricardo Mitchell.

Quick Steps

  1. Try a different phone on the line to rule out phone problems.
  2. Test each outlet to see if they're all affected.
  3. Call the line from an outside phone to see if it rings or gets a busy signal.
  4. Access the terminal box on the outside.
  5. Use a working phone to test the outlet inside the terminal.
  6. Use a multimeter to test the wires inside the terminal and other outlets.
Method 1
Method 1 of 4:

Troubleshooting Phone Issues in Your Home

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  1. Check each phone that’s plugged into your phone line to make sure they’re all securely on the hook. To be sure, pick up the receiver and place it back down on the base. [1]
    • This makes sure your line isn’t interrupted by a phone that’s off the hook and that you’re not still currently on a call.
  2. If you’re using a cordless phone, the battery may be low. Place it on the charger and allow it to charge for at least 15 minutes. Then, test the phone again to see if it works. [2]
    • If you have a cordless phone, it’s possible the phone line isn’t working because the battery is dead.
    • If you have a regular corded phone, use it to test the phone line without having to wait for the cordless phone to charge.
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  3. Unplug the phone cord and examine it to make sure it’s not broken. Plug it back in and make sure the plug feels stable rather than loose or wobbly. [3]
    • If the plug is damaged, that could be your issue. Get a new phone cord to see if your phone line will work.
  4. If you have an extra phone available, unplug the phone you’re currently using. Then, hook up the extra phone to see if it works. Hold the receiver up to your ear to listen for a ring tone. [4]
    • This helps you rule out your phone as the source of the problem.
  5. If you have more than one phone jack, test each jack individually to determine if it’s a particular jack or if the phone line itself is having issues. First, unplug all of the devices in your home, including phones, fax machines , and modems. Then, use a phone to test each jack to see if only one is affected. [5]
    • If only one jack is affected, call your phone company to get a service call for that individual jack. This might save you money since you know where the problem is occurring.
  6. Use your cell phone to call the phone line you want to check. Alternatively, ask a neighbor to call your phone. Listen to see if your phone rings or if you get a busy signal. [6]
    • This can help you see if the phone can receive calls but not make them.
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Method 2
Method 2 of 4:

Assessing the Outside Phone Lines

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  1. Go outside your home and look for the cables attached to your home. You’ll see a thin black cable that runs from a box on the telephone pole to your home. Locate this cable so you can find your phone box. [7]

    Tip: If you have a BT phone line, the test socket is typically inside the main socket. Instead of going outside, unscrew the plate on your main socket to access a text socket inside. Then, plug your phone into the test socket to see if you get a dial tone. [8]

  2. Once you locate the phone cord, follow it with your eyes to find the spot where it connects to your home. Look for a small box on the exterior of your home that has a plate screwed over it. [9]
    • You’ll see the phone cord sticking out of the box.
    • If your home is very old, you may not be able to open the phone line box. In that case, call the phone company to request a service call.
  3. Look for the screws that hold the lid on the phone line box. Unscrew and remove the screws, then take off the plate. This gives you access to the phone lines and a jack where the external phone line connects to your internal line. [10]
    • Check that you’re using the right type of screwdriver. The screws may be flat head or Phillips head.
  4. Inside the box, you’ll see a bunch of wires and a phone jack with a phone cord plugged into it. Do a visual inspection to find the spot where the phone cord is plugged in. [11]
    • This is where you’ll test your phone line.
  5. Squeeze the plug and pull it out of the jack. Leave the plug hanging because you’ll plug it back up after you test the line. [12]
    • This unplugs the internal phone line from the exterior phone line.
  6. Put the plug on the phone cord that’s connected to your test phone into the jack. Make sure that the plug is securely attached. [13]
    • This plugs your phone directly into the exterior phone lines.
  7. Hang up your phone to make sure the line is clear. Then, see if there’s a dial tone.
    • If you hear a dial tone, the problem with your phone line is inside your house. If this is the case, you’ll likely need to get the phone line inside your home repaired.
    • If you don’t hear a dial tone, there is likely an issue with the phone company’s lines that are coming to your home. Call your telephone provider and request that they check your line.
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Method 3
Method 3 of 4:

Testing the Signal and Wiring with a Multimeter or Voltmeter

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  1. The multimeter or voltmeter test will not work if any devices are plugged into your phone line. Go around your home and unplug every device from the jacks before conducting the test. [14]
    • According to Mitchell, both a multimeter and voltmeter can test your phone line’s continuity.
    • Additionally, a voltmeter can test whether or not the phone company’s signal is reaching your home.
  2. Locate the phone line that connects to the outside of your home, then follow it to the square box on the side of your home that houses the phone wiring. Use a screwdriver to open the box and remove the cover. You’ll see the phone lines inside. [15]
    • Leave everything connected and plugged up if you’re using a voltmeter to test for a signal.
  3. This is optional, but can confirm that you’re getting a signal from the phone company. Set your voltmeter to volts or VDC. Then, touch the negative probe to the red telephone wire and the positive probe to the green telephone wire. Check the meter to make sure there’s a voltage reading, which is typically 45-48 mV. [16]
    • If there’s no reading, or it’s zero or near zero, you likely aren’t getting a signal from the phone company. Call the phone company to schedule a service call for repairs.
    • If you have a second line, you can test the second line by touching the negative probe to the yellow wire, and the positive probe to the black wire.
  4. Unplug the phone cord from the exterior phone jack and let it hang. Then, disconnect the colored wires to open the circuit. Make sure that none of the wires are touching. If they do touch, the circuit will close, and you won’t be able to test for continuity. [17]
    • This will temporarily disconnect the phone line from your home so you can test the wiring.
  5. Follow the instructions that come with your device to change the Continuity setting. Usually, you will need to set the device to read Ohms (Ω). This will allow you to check if any of the wires inside your home are touching. [18]
    • Both multimeters and voltmeters have a continuity setting.
  6. For a multimeter, touch the leads to the wires that line up with them to reduce the risk of the wires crossing. If you’re using a voltmeter, touch the negative probe to the red wire and the positive probe to the green wire. [19]
    • If you have a second line, you can test the second line by touching the negative probe to the yellow wire, and the positive probe to the black wire.
  7. You should get a reading or your multimeter will beep. According to Mitchell, if there is no continuity, it’s a sign that the wires are touching somewhere in your home or that you have a jack that’s burnt out. When the wires touch, it creates a phone line fault that prevents your phone service from working properly. [20]
    • Generally, you’re responsible for repairing the wiring inside your home. Your phone company may send a service person out to fix the wiring at your cost. However, they might recommend hiring a general contractor to access wiring inside your walls.
    • If you are unsure if your multimeter is working properly, you can test it by measuring the volts from a battery or testing the continuity of a fuse.
  8. Check the external wiring first. If there are no connectivity issues, it’s likely that your wiring is not faulty. If you detect a connectivity issue, test the wiring that goes into each phone jack to see where the issue is occurring.
    • When you call the phone company, tell them that your internal wiring is not showing any problems or specify which telephone jack appears to be the issue. This may help them fix the problem faster and could save you money since you know the problem isn’t on your end.
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Method 4
Method 4 of 4:

Checking if a Phone Line is Busy

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  1. The best way to find out if a line is busy is to call it. Use your mobile phone or a landline to make the call. If the line is open, you’ll hear the line ringing. If you hear a busy signal, someone is likely using that phone line. You’ll also get a busy signal if the phone was accidentally left off the hook or someone else is dialing the number at the same time you are.
    • In some cases, you might get a fast busy signal or a busy signal after a ring if your phone number is blocked.
    • It’s best to try the number several times before you assume something is wrong. However, spread out your calls so you aren’t constantly dialing the number.
    • It’s possible that there is a fault in the phone line if you’re constantly getting a busy signal. [21]

    Tip: If you’re having trouble reaching someone, check that you have the correct number. It's super easy to write or type a number incorrectly.

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      Things You’ll Need

      Troubleshooting Connectivity Issues in Your Home

      • Extra phone (optional)

      Assessing the Outdoor Connection

      • Screwdriver
      • Standard corded telephone

      Testing the Signal and Wiring with a Multimeter or Voltmeter

      • Multimeter or Voltmeter
      • Screwdriver

      Checking if a Phone Line is Busy

      • Phone

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      References

      1. ↑ https://business.bt.com/help/article/phone-line-and-services/faults-and-repairs/i-have-a-fault-on-my-phone-line-how-do-i-test-my-equipment-or-wiring/
      2. ↑ https://business.bt.com/help/article/phone-line-and-services/faults-and-repairs/i-have-a-fault-on-my-phone-line-how-do-i-test-my-equipment-or-wiring/
      3. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      4. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      5. ↑ https://business.bt.com/help/article/phone-line-and-services/faults-and-repairs/i-have-a-fault-on-my-phone-line-how-do-i-test-my-equipment-or-wiring/
      6. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      7. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      8. ↑ https://business.bt.com/help/article/phone-line-and-services/faults-and-repairs/i-have-a-fault-on-my-phone-line-how-do-i-test-my-equipment-or-wiring/
      9. ↑ https://www.youtube.com/watch?v=vg7LixY7c1M&feature=youtu.be&t=30
      1. ↑ https://www.youtube.com/watch?v=vg7LixY7c1M&feature=youtu.be&t=40
      2. ↑ https://www.youtube.com/watch?v=vg7LixY7c1M&feature=youtu.be&t=48
      3. ↑ https://www.youtube.com/watch?v=vg7LixY7c1M&feature=youtu.be&t=50
      4. ↑ https://www.youtube.com/watch?v=vg7LixY7c1M&feature=youtu.be&t=55
      5. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      6. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      7. ↑ https://www.doityourself.com/stry/how-to-test-a-phone-line-with-an-analog-voltmeter
      8. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      9. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      10. ↑ https://www.youtube.com/watch?v=sD4eOB7Qi04
      11. ↑ https://www.naturalhandyman.com/iip/inftelephone/inftel1.html
      12. ↑ https://business.bt.com/help/article/phone-line-and-services/faults-and-repairs/number-calling-permanently-engaged-could-this-be-fault/

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