You are all familiar with special service codes, such as 411 for local directory assistance, 611 for repair service, and 911 as the universal emergency number. In addition to these are a number of N00 codes called service access codes. The most familiar of these is the 800 code used for toll-free calling, where the called party, rather than the calling party, is charged for the call. This code is an important marketing tool for businesses that allows customers to call toll-free to place orders, obtain customer assistance, and the like. Within an NPA there can be only 800 NXX codes, and within an NXX only 10,000 line numbers can exist. The explosive growth of 800 services has brought about the imminent depletion of 800 numbers. Consequently, Telcordia Technologies identified the additional codes for use with toll-free services.

The 888 codes for toll-free service were introduced in March 1996, and the 877 codes were introduced in January 1997. The introduction of Personal communications services (PCS) opens up the opportunity for people to use a single number for telephone, fax, paging, and other services. This number will follow the person everywhere, just as a cellular customer can be reached while roaming. Telcordia Technologies has already begun assigning blocks of numbers to carriers for PCS use from the 500 service access code