PURPOSE: To improve the utilizing efficiency of a transmission line and the reliability by giving periodically or unperiodically a signal used to synchronize a clock pulse of each transmission and reception sides to a reception side, eliminating the need for the transmission of a synchronism clock and sensing plural number of times as to one bit in the timing related to the clock pulse at the reception side, and deciding a binary data by means of majority decision logic.

CONSTITUTION: A reset pulse to section between a frame is included in a transmission signal (train). a reset pulse discriminating circuit to which the transmission signal is inputted discriminates and extracts the reset pulse from this transmission signal and gives it to a synchronizing clock circuit 7, which generates a clock signal for synchronizing the transmission signal, while being triggered by a reset pulse input. a clock pulse shown in B is obtained by a received reset pulse, interruption is applied at the trailing of the clock pulse, n-times scanning is attained as shown in C, and the discrimination of "0" and "1" is conducted by the majority decision logical as the result of scanning.