In the North American Numbering Plan (NANP), 500 service is intended to support premium follow-me personal communications services, which are defined as a set of capabilities that allows some combination of personal mobility, terminal mobility, and service profile management. 500 service is designed to allow the subscriber to select from a menu of services and to initiate or receive calls at any terminal, fixed or mobile, across networks, regardless of geographic carrier. 500 numbers can be protected by the personal identification number (PIN) for network and feature access. As 500 numbers are not locationspecific and are transportable across carriers and carrier domains, one number theoretically can be retained for life. 500 service numbers are in the format 500-NXX-XXXX. See also NANP.