| 摘要 |
PURPOSE:To prevent the content of communication from tapping continuously by a 3rd party by switching the frequency of a radio channel used between a mobile body and a radio base station at each prescribed time. CONSTITUTION:An automobile telephone exchange station 4 operates a timer circuit 8 based on a talking start signal to start the count of a time T. When the time T is counted by the timer circuit 8, after the automobile telephone exchange station 4 selects one of idle communication channels of a small radio zone, the station executes a wire continuity test with a radio base station 2 as to a communication channel. When the result is excellent, a communication channel switching signal is sent to select a new communication channel f3 through a communication channel f2 in use at present. A mobile equipment executes the radio continuity test with the radio base station in response thereto after a new communication channel is selected. Thus, the privacy of communication is enhanced without using a special privacy equipment. |
