Term used typically to represent the 4th-6th digits of the ten-digit telphone number (N = any digit 2-9, X = any digit 0-9).

 Service Provider Identification Number. (See NPAC SPID.)

A - Alt SPID: The four-digit identifier of a second service provider associated with a telephone number or thousand block.  It identifies the wholesale service provider customer to which the PSTN serv [..]

 Abstract Syntax Notation One

 Alliance for Telecommunications Industry Solutions

 A group of 1,000 contiguous telephone numbers in the range NPA-NXX-X000 through NPA-NXX-X999. Usually referred to as a "pooled bock" even when not actually assigned by the nation nu [..]

 A Bell Operating Company was a company owned or controlled by AT&T prior to the 1984 AT&T divestiture action.

 A private Canadian Corporation established to facilitate the development and provision of a Local Number Portability (LNP) system for use by Canadian Carriers.

Identifies a group of vertical service features such as Caller ID (calling number delivery), Calling Name delivery, and call filtering (either to accept or to reject calls from specified numbers).  (S [..]

 Competitive Local Exchange Carrier. The land line carrier entrant to a market where there is already an incumbent LEC providing local phone service.