PURPOSE: To perform good data communication without outputting extra bits by providing a demodulating means which discriminates and shapes a reception input signal to obtain a data signal, a discriminating means which obtains a discrimination output signal, an AND circuit which obtains the AND output between the input and the output of a delay circuit as a control signal, and a gate circuit.

CONSTITUTION: A reception input signal 21 inputted to an input terminal 1 is converted to a DC signal by a rectifying and smoothing circuit 8 and has the level discriminated byha comparing and shaping circuit 9 and has the waveform shaped to obtain a discrimination output signal 23. This output signal 23 is delayed in a delay circuit 10 by a prescribed time to output a carrier monitor signal 24 to an output terminal 11, and the discrimination output signal is inputted to the other input of an AND circuit 12, and the output of the AND circuit is used as the control signal to the gate circuit. After data communication, the gate circuit is so operated that extra bits included in a data signal 22 are not outputted to a reception output terminal 7 and the signal state of the output terminal 7 is held in the mark state, and a reception data signal 27 is obtained.