PURPOSE: To enable information to be transmitted with simple installation by supplying an electric power necessary for a device of moving body side to make normal operation through electromagnetic induction.

CONSTITUTION: The output of the oscillator 5 of a ground device 2 is supplied to a coil N1, and a voltage is induced in the coils N3, N4 of a device of moving body side 3 which are electromagnetically coupled. The voltage induced in the coil N4 is rectified by a rectifier 9 and is applied as a DC voltage to a parallel-series converter 11. The parallel inputs by an information setter 10 is converted into a series code by the converter 11 and the code is sent to a modulator 12. The modulator 12 changes the reactance of the coil N3 according to the output of the converter 11. The phase deviation in the circuit current at this time is detected with a phase detector 7 and is led out as the parallel outputs by a series-parallel converter 8.