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An area code overlay is a numbering plan area (NPA) in the North American Numbering Plan (NANP) that has multiple area codes assigned. Overlay complexes are used to add central office prefixes in an NPA to increase the number of available telephone numbers .
A numbering plan area with multiple area codes is called an overlay. Area codes are also assigned for non-geographic purposes. The rules for numbering NPAs do not permit the digits 0 and 1 in the leading position. [1] Area codes with two identical trailing digits are easily recognizable codes (ERC).
In telecommunications, an area code overlay complex is a telephone numbering plan that assigns multiple area codes to the same geographic numbering plan area (NPA). Area code overlays are implemented in territories of the North American Numbering Plan (NANP) to mitigate exhaustion of central office codes in growth areas. The method has been in ...
In California and New York, because of the existence of both overlay area codes (where an area code must be dialed for every call) and non-overlay area codes (where an area code is dialed only for calls outside the subscriber's home area code), "permissive home area code dialing" of 1 + the area code within the same area code, even if no area ...
Telephone numbers in area code 678 were first assigned to customers signing up for new telephone service on January 15, 1998. On September 2, 2001, area code 470, was added to the 678 overlay area of area codes 404 and 770. [1] Telephone numbers from the NPA were assigned after exhaustion of area code 678.
As a result, in the early 1990s, the North American Numbering Plan Administrator (NANPA) introduced another method for exhaustion relief: the area code overlay. This method assigns multiple area codes to the same numbering plan area, so that existing subscribers can keep established telephone numbers. Only new accounts and extra lines receive ...
Public resistance to the introduction of new area codes, whether as overlay complexes (which allowed customers to keep their existing numbers, but broke seven-digit local calling) or by area code splits (where the area code of existing numbers was changed), prompted the FCC and state commissions to introduce thousands-block number pooling, i.e. the allocation of number space in blocks of only ...
A few area codes not part of any overlay complex nonetheless require ten-digit dialing if part of the local calling area is within an overlay complex. For example, the Fort Knox Army base in Kentucky is served by area code 502, but its local calling area includes cities that are served by the 270/364 overlay complex. As a result, Fort Knox ...