North American Numbering Plan - Currently a seven-digit address to identify each network station (telephone). The address takes the form NXX-XXXX where: N can be any digit 2 through 9 and X can be 0 through 9. The arbitrarily assigned NXX portion of the address identifies the customer location where the station is homed. It cannot be the same as the NXX digits assigned to the same switch for public network (such as POTS) use. The XXXX digits are the numbers of the individual station at the customer location.

This address is preceded with a three-digit area code, and for dialing since the 1984 divestiture, the full dialing address is:

10XXX where XXX identifies the specific carrier. The dialing sequence is 10XXX+(0/1)+7/10 digits (D), where X can be any digit from 0 to 9. The 7/10 digits dialed must conform to the North American Numbering Plan (NANP).