PURPOSE: To use a titled transmitter even in water and under a bad environment, by energizing a magnetoresistance element with a coil and sealing the transmission and the reception side with a nonmagnetic metal or a plastic housing.

CONSTITUTION: A current corresponding to an input signal flows from an input section 4 and a current controller 5 to a coil L with a signal entered in an input terminal C of a transmission side circuit 1, and magnetic flux is generated from the coil intermittently. This intermittent magnetic flux change is detected by a bridge circuit B constituted with a magnetoresistance element of a reception side circuit and this detection signal is amplified at an amplifier A. An output of the amplifier is inputted to a switching circuit S as compared with a reference voltage and switched and inputted to an output circuit OT.