A narrowband radio system and method for use in wireless communication systems. Preferred embodiments are designed to provide data communication links between users, referred to as “endpoints”. Endpoints in many embodiments include wireless radio modems. In preferred embodiments many or all of these links are two-way data communication links. Endpoints (typically “human users or computer systems”) can send data to the radio modems, and the radio modems can send data to the endpoints. In typical systems, the radio modems are connected to machines that are configured to respond to data communication. Computers are programmed with special protocols designed for efficient communication of information through the narrow band channels among users of the wireless trunking system.