PURPOSE: To make it possible to adjust a phase even when there is information from a mobile station to a master station via a subordinate station, by providing the subordinate station with a circuit which detects a downward signal varying in information length and by making a phase adjustment of a downward circuit only.

CONSTITUTION: Subordinate station 27 is provided with circuit 21 which detects a data signal, as to the output of demodulator 16, varying in information length according to time and on the detection of the variation by circuit 21, alarm information is sent by gate 20 to master station 26 to generate 25 an alarm. Here, downward information I0 is modulated 14 via phase-adjusting delay circuit 13 and supplied via downward circuit 15 to subordinate station 27, where it is demodulated 16 and sent to mobile station 18 via transmitter 17, and upward information from mobile station 18, on the other hand, is received 19 by subordinate station 27, modulated 22 via gate 20, and demodulated via upward circuit 23 to reach master station 26. Because of this constituion, setting the delay value of circuit 13 to an adequate value after decision 25 on variation in the delay value of the circuit allows an adjustment so that the delay phase value from the input of circuit 13 to that of transmitter 17 will be constant all the time.