NPA code | Article about NPA code by The Free Dictionary
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NPA code(Numbering Plan Area code) The area code of a telephone number in the NPA system. The first NPA codes used 0 or 1 as the center digit, such as 201, 212, 301, 312, etc., designated as "N0/1X." After July 1, 1995, all digits 0 through 9 are valid as the center digit, designated as "NXX." See NPA and NPA/Nxx.