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Testing, Repairing and Installing Home telephone Wiring - Network Interface Device

The Network Interface Device

When working in or near that NID, be sure to be careful.  Aside from being the device where the telephone service wire connects to the inside wire, the NID also provides electrical protection through the electrical grounding system on the customer's premises, so any work you do on the NID could have an affect on how these electrical systems are grounded.

NOTE: The NID and/or Network Interface Device is maintained and installed by your local service providers.  In many cases, there may not be a charge for a new installation, however, if you wish to have your NID moved for convenience or aesthetics or if you have damaged the NID, a charge will typically apply.  Contact your local service provider for more information.

The device itself will have 3-5 posts that interconnect the telecommunications company’s wire to your inside wire.  If the NID is located outside your house, it will have a plastic cover.  You will need to remove this cover to access the wiring, but since this cover is an important protector of the telephone equipment, it must be properly reinstalled after your work is completed.  The telephone company side of the NID is locked and you should not attempt to open it.  

A typical network interface device will include a “test jack” that looks like a typical modular telephone outlet, as is show here: 

Network Interface Device

By unplugging the short wire and plugging a working phone directly into this jack, you can determine whether a problem is in the home (wiring, jacks or telephone equipment) or in the telephone company’s lines.  It is recommended that you use a wired telephone (i.e., not a cordless phone) for this test since a cordless phone may actually be the cause of static or other noise on the line.  If the phone does not operate using the test jack, you should call your telephone company because the trouble is in the network leading up to your network interface device.  If the phone operates when you have plugged it into the test jack, the fault is in the inside wiring, jacks or telephone equipment and is the customer’s responsibility.   

If you do hear a dial tone when testing from the test jack, you have three choices:

  • Call your local telephone company to receive a quote to repair your inside wire or to place a repair order (note that some companies do offer repair insurance programs that allow you to pay a monthly fee to have your inside wire covered by a repair plan. Contact your local provider if this service is of interest to you).

  • Call a contractor to repair the service.  Contractors are listed in your telephone directory.

  • Repair the trouble yourself (this guide is directed towards those who choose this option)