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NXX often denoted NPA: Numbering plan area code The first NXX block is the numbering plan area code. When the second and third digits are the same, the code is an easily recognizable code (ERC). ERCs designate special services; e.g., 800 for toll-free service. The NANP is not assigning area codes with 9 as the second digit. [37]
Local number portability allows a number to be moved to a different carrier or a different wire center within the same rate center. [4] A landline provider typically will not allow a cross-town move to a different rate center under the same number at standard rates; possible alternatives include expensive foreign exchange service or a nomadic class of service such as voice over IP or a mobile ...
The North American Numbering Plan (NANP) divides the territories of its members into geographic numbering plan areas (NPAs). Each NPA is identified by one or more numbering plan area codes (NPA codes, or area codes), consisting of three digits that are prefixed to each local telephone number having seven digits.
In the administration of the North American Numbering Plan, central office code protection is a numbering policy for maintaining local seven-digit dialing in communities that extend on both sides of the boundary line between multiple numbering plan areas (NPAs), such as in cross-border towns on state lines.
From 1947 to 1995, all NPA codes were distinguished with the digits 0 or 1 in the middle position. This provided the traditional format N 0/1 X, where N is any digit from 2 to 9, and X is any of the ten numerals. This format provided a set of 160 combinations, but only 144 were in use for geographic NPA codes.
The Local Exchange Routing Guide (LERG) is a database of telecommunications numbering resources for use in the administration and operation of the North American Numbering Plan (NANP) by the NANP administrator (NANPA) and telecommunications service providers.
Thus, NXX is a number from 200 through 999, while XXXX is a range from 0000 through 9999. The first three digits of a telephone number are the numbering plan area code (NPA code, or simply NPA). The next three, NXX, identify the central office and the last four digits are the line number of an individual office.
AT&T divided the United States and Canada into numbering plan areas (NPAs), and assigned to each NPA a unique three-digit prefix, the numbering plan area code, which became known in short-form as NPA code or simply area code. The area code is prefixed to each telephone number issued in its service area.