The NID is the point where our outside wiring (the provider network) connects to your inside wiring (the subscriber network). Some customers call it the telephone box or network box, while technicians usually call it simply "the NID."
These boxes are usually about 6 by 9 inches and gray (or painted to match the house). It will most often be attached to the outside of the home near the electric meter. Sometimes it is found in the basement or attic. It's usually clearly labeled "Network Interface Device" or "Telephone Network Interface" on the outside.