Abstract: Key switches, a plane type CRT display, a modulator, a demodulator, etc. are arranged in a control board mounted on a steering wheel, while a TV camera, a character information generator, a modulator, a demodulator, etc., are arranged on the side of the vehicle body. Electric circuits on the control board and the vehicle body are interconnected through slip rings and brushes, and display information is transmitted from the vehicle body side to the control board in accordance with operation of the key switches on the control board, thus permitting the information to be displayed on the control board. A signal corresponding to operation of the key switches and a display information signal are made to have different frequencies from each other and then transmitted through the same line in a superimposed fashion.