PURPOSE: To transmit stably a signal by providing a diode for preventing reverse flow and a diode for clamping and further providing a resistor for suppressing an interference wave to a transmission line to preclude the possibility of chattering in the output signal of a logical circuit element for reception.

CONSTITUTION: The diode D1 for preventing reverse flow is provided to a power supply voltage line 3 tying the power supply section E1 and the reception logical circuit element 2 so that the anode is connected to the power supply section E1 side. Resistors R5, R6 for suppressing an interference wave to suppress the peak value of the interference wave caused at the rise or fall of an output signal are provided respectively near logical circuit elements 1, 2 in a transmission line 10. The diode D3 for clamp is connected between the cathode of the diode D1 for preventing reverse flow and the transmission line 10 so that the anode is connected to the transmission line 10 side.