Definitions for "NNX"
Keywords:  nxx, central, office, former, digit
Older form of central office code where N is any digit from 2 to 9 and X is any digit from 0 to 9.
Former three-digit location code which represented a central office. Now in NXX form, the available number of CO codes has been increased by permitting 0 and 1 as second digits in some circumstances.
Network numbering exchange. The second set of three digits of a telephone number that designates a number to a specific central office.