JPS6354263B

PURPOSE:To simplify the control and the device for setting a circuit, by using a frequency designated by a mobile station to detect the presence or absence of the free line signal with an astatic circulating system. CONSTITUTION:The radio base stations S1-Sn modulate the electric wave designated previously with the free line signal in an idle mode and then transmit the electric wave between the radio base stations with a certain timing and shifting mutually the frequency or the timing. A mobile station 17 retrieves the free line signal with an astatic circulating system and then discontinues the retrieval when the free line signal is detected. The radio circuit of that moment is used for a communication circuit. As a result, the station 17 can select monotonously a radio base station although the stations S1-Sn exist close to each other. Thus no control is required at a control station 15.