The invention is comprised of a coil group arranging a plurality of terminal-integrated type coils, formed by bending a metal sheet in a preset development form and having a predetermined positional relationship, and a magnetic material burying therein the coil group. When the friction clutch is in a half clutch state and the slip of the driving wheel is detected at the time of starting of the vehicle, the clutch actuator control section controls the clutch actuator so as to change a pushing force of the friction clutch and thus to keep the rotation speed of the engine at a fixed level. The tomographic image generating unit is configured to generate a tomographic image in accordance with each of the directions of the ultrasonic beams. The threshold level of the adjustable voltage clamp circuit varies with respect to the amount of slope compensation provided to the voltage regulator. AC amplifiers can be used as RF photocurrent amplifiers.