In a geographic region that contains a trunking communication system and a cellular communication system, where the coverage area of each system substantially overlaps, a method that enables a communication unit to operate in either system is disclosed. Normally in accordance with the present invention,...http://www.google.com/patents/US5179721?utm_source=gb-gplus-sharePatent US5179721 - Method for inter operation of a cellular communication system and a trunking communication system
