PURPOSE: To prevent useless malfunction even when an infrared-ray pulse from a re-emitting section is returned to a light receiving section by blocking the generation or the transmission of an electric signal corresponding to the returned light.

CONSTITUTION: A monostable multivibrator 6 capable of no retriggering as a means blocking the production or the transmission of an electric signal for a prescribed period after the generation of the electric signal is provided between the light receiving section 1 and the re-emitting section 4. Even when an infrared-ray pulse train from the re-emitting section 4 is returned to the light-receiving section 1 and a differentiation pulse train takes place, it is blocked by the monostable multivibrator 6 and no useless infrared-ray pulse train is generated. Thus, a controller 5 is remotely controlled surely without causing malfunction.