RADIO TELEPHONE SYSTEM

摘要

A portable duplex radio telephone system includes base station transmitters having a predetermined base transmission range, and a plurality of portable or mobile units each having a predetermined maximum transmission range shorter than the base transmission range. Satellite receivers are deployed about each base station for receiving transmissions from the portable units. The base station transmitters transmit signals on a signalling channel and on at least one communications channel. The portable receivers have means for scanning the base station transmitter signalling frequencies and for tuning to the signalling frequency associated with the strongest signalling signal received from the base transmitter. When communication is initiated, the portable transmitter and receiver are automatically retuned to one of the communications channels as determined by the strongest received signalling frequency and by channel availability. Means are also pro vided to continuously locate a portable unit and switch the operating frequency thereof as the portable unit moves between base station transmitter coverage areas. Further means are provided to reduce the output power of each portable transmitter to the minimum satisfactory level in order to reduce battery drain and interference.