STUFF CONTROL CIRCUIT

PURPOSE:To operate a normal stuff insertion even if more than the two pulses of a stuff detecting signal are obtained during one frame period in a stuff control circuit which is used at the transmission side of a digital transmitting device, etc., by a stuff synchronization system. CONSTITUTION:A beat frequency detecting circuit 2, a beat number counter circuit 3, an up-down counter 4, a counter output synthesizing circuit 5, a stuff instruction circuit 6 and a FIFO memory reading control circuit 7 are provided, the up-down counter 4 is counted-up by the stuff detecting signal S1 which is outputted from the beat number counter circuit 3 and the up-down counter 4 is counted-down by a stuff instruction signal S3 which is outputted from the stuff instruction circuit 6 so that a stuff request signal S2 is normally being transmitted to the stuff instruction circuit 6 so far as the value of the up-down counter 4 is not zero. Thus, the normal stuff insertion is operated even if more than the two pulses of the stuff detecting signal are obtained.