PURPOSE: To confirm whether a broadcast has been executed normally or not by comparing the number of times by which a transmitting output level has exceeded a prescribed value in a master station, and the number of times by which a broadcasting signal level has exceeded a prescribed value in a slave station, by the master station.

CONSTITUTION: In a master station 1', a sound signal is amplified by an amplifier 5, and thereafter, one is applied to a transmitter 6, and transmitted from an antenna 19. The other is inputted to a counter means 20, a signal (b) rectified by a rectifying circuit 23 is inputted to a comparing circuit 24, and a pulse C is outputted only when exceeding a reference voltage Vr, and counted by a counter 25. The signal received by an antenna 19 of a slave station 9' is broadcast from a loudspeaker 12, a broadcasting sound is inputted to a counter means 22 through a sound collecting microphone 14 and an amplifier 15, compared with the reference voltage Vr and counted in the same way as the circuit of the master station, and count data is outputted from the antenna 19 through a data modulating circuit 17 and a transmitter 18. This signal is inputted to a deciding circuit 21 through the antenna 19, a receiver 7 and a data demodulating circuit 8 and compared with the number of couns of the transmission time in the master station 1', and whether a broadcast is normal or not can be confirmed.