The telephone Network Interface Device (NID) is what connects your home telephone lines to the telephone company’s network. It is usually a small gray box located on the exterior of your home. It usually contains a modular phone plug that you can use for testing the line. They need both inside testing and outside testing. In some older installations, you may not have a NID. Instead, you will find a “protector block”, a small plastic covered box where the cable coming out of your house connects to the phone company’s cable leaving your house. The protector block serves the same purpose as the NID, but does not provide a modular jack where you can check if you are getting dial tone from the phone company.
Plug a corded telephone into each of your phone jacks. Check for dial tone or static. Repeat process using a different corded telephone to make sure the first phone is not the cause of the problem. Remove the plug from each jack in the NID. Plug in a working, corded phone. If you hear a dial tone, make a test call. If your call goes through, the problem is inside your home. This is where having a service on your phone plan called a ‘inside wire maintenance plan’ is beneficial! It is usually only a few dollars a month, and if there is a problem with the inside wiring, the phone company will fix it for free. Otherwise, you will have to pay for the service call!
Each telephone number in your home should have a jack with a dial tone in the NID. If there is no dial tone or static on the line, the problem is likely in the line outside your home. Now repeat this step with a different phone. That way you can make sure that the first phone is not the cause of the problem. By taking a corded phone to the NID on the outside of your home, and testing your phone from the phone jack in that box, you will be able to tell the phone company if the problem is inside or outside the home. If you do not get a dial tone when using the outside NID box, then the problem lies in the phone company wiring somewhere.
To use ADSL or other high speed Internet you need to have an up-to-date NID. It is possible that you will need a new Network Interface Device if you happen to have an older one. Apartments and office buildings should have up-to-date NIDs. Older residences are most likely the ones that will need this free upgrade.