North American Number Plan (NANP)

A plan for the allocation of unique 10-digit address numbers. The numbers consists of a 3-digit area (numbering plan area) code, a 3-digit office code, and a 4-digit line number. The plan also extends to format variations (e.g., 3-digit and 7-digit address), prefixes (e.g. , 1, 0, 01, and 011), and special code applications (e.g., service access codes). [T1.104-1988]

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