PURPOSE: To prevent the structure of a steering wheel part from becoming complicate and increasing in capacity by arranging a key switch and a surface display device on a steering operation board and providing only a demodulator which demodulates display information and a modulator which outputs key input information on the operation board.

CONSTITUTION: A constant voltage power source device 70, microcomputer unit (CPU1) 80 which controls operation on the steering operation board, key switch 90, FSK modulating and demodulating circuits 100 and 110, microphone MC, differential amplifier DFA, FM modulator, monitor television TV as the surface display device, tuner TU, distributor 190, etc., are arranged on the steering operation board. Further, other circuits or a control unit is provided on the side of a vehicle body and both are connected together by an electric connecting means consisting of two brushes for a signal and a power source and a slip ring.