SYNCHRONIZING SYSTEM

PURPOSE:To restore quickly synchronization and to prevent the efficiency of transmission from reduction by forming a synchronization deciding means and a means for receiving a synchronizing signal retransmission request and sending a new synchronizing signal from the transmission side to the reception side to reestablish synchronization. CONSTITUTION:A transmission signal is ciphered by an adder 2 on the basis of a false random number signal outputted from a false random number genera tor 1, outputted as a transmission signal 101 and inputted to an adder 4 through a switching circuit 8. On the other hand, a false random number signal outputted from a false random number generator 3 is inputted to the adder 4 and added to the signal 101 and a deciphered receiving signal 102 is outputted. The signal 102 is inputted to a synchronization monitoring and deciding circuit 5, a decided result output signal 105 is outputted, and if the signal 105 is abnormal, a request signal 106 is transmitted from a synchronizing signal retransmission requesting circuit 6 to a transmission side synchronizing signal sending circuit 7. Then, a synchronizing signal 107 is newly transmitted from the transmission side to the reception side through the circuit 8, so that synchronization can be se cured and the efficiency of transmission can be prevented from reduction.