An apparatus and method for telecommunications network local number portability supports service provider portability, location portability, and service portability. A subscriber is assigned a nongeographic subscriber number that is uniquely mapped to a location-based geographic terminal...http://www.google.com.au/patents/US5764745?utm_source=gb-gplus-sharePatent US5764745 - Apparatus and method for local number portability using nongeographic subscriber numbers 
