PURPOSE: To decrease the number of channels of a recording device necessary for sound recording and reproduction by providing a circuit which varies the level of timing pulses for channel discrimination to an acoustic sounding device which operates sounders in series with time.

CONSTITUTION: The circuit 14 which varies the level of timing pulses Tr1WTrn is provided and a comparator 17 which discriminates the level of the timing pulses is also provided; and the level of each specific timing pulse Tr is varied and respective timing pulses are put together and recorded on a magnetic tape device 19. When the timing pulses are reproduced, the level of a specific timing pulse is discriminated by the comparator 17 to reproduce timing pulses of respective channels. Consequently, received signals 1W(n) are recorded by requiring channels as many as transmitter receives, but only one channel is required to record the timing pulse in this case, thereby reducing the number of channels for the recording and reproduction of the magnetic tape device on the whole.