Abstract: An automatic car-speed controller is provided with a car-speed sensor, a command switch, a car-speed memory, an actuator, a control circuit for controlling the actuator, and a prohibition circuit for preventing a driving motor of the actuator to rotate in the accelerating direction at the time of cancelling car-speed control or occurrence of some abnormality in the control circuit or the like, or a discrimination circuit for detecting whether a first limit switch is normal or not without driving a throttle in the opening direction.

Abstract: An automatic car-speed controller is provided with a car-speed sensor, a command switch, a car-speed memory, an actuator, a control mechanism, and a holding circuit for cutting off an electric current to the actuator according to a braking operation and maintaining the actuator in its nonworking state till the actuator returns to its working state in response to a cruise command signal from the command switch in addition to the control mechanism. According to this controller, it is possible to release the actuator rapidly from the automatic car-speed controlling state in response to the braking operation even if the trouble occurs in the control mechanism.

Abstract: A car-speed control system is provided with a car-speed sensor, a command switch, an actuator having an electromagnetic clutch, an actuator-driving circuit, a clutch-driving circuit, a car-speed memory, a controller and a comparing circuit for comparing voltage level with reference voltage at the time of changing the electromagnetic clutch to its unexcited state and for changing the actuator-driving circuit to its non-driving state if the voltage level of the clutch-driving means is higher than the exciting voltage of the electromagnetic clutch.

Abstract: An automatic car-speed controller is provided with a car-speed sensor, a command switch, a car-speed memory, an actuator, a driving motor, an abnormality detector for detecting an abnormality in an electromagnetic clutch of the actuator by detecting the time required for returning a throttle to the fully closed position from the position at which the electromagnetic clutch is released, and a control system for making the actuator inoperative when the abnormality detector detects an abnormality in the electromagnetic clutch.

Abstract: A motor driving device for rotating a motor in forward and reverse directions which includes a switching circuit arranged in an H-bridge connection with both terminals of the motor, a controlling circuit, and an interception device provided on the respective terminal sides of the motor. The switching circuit includes two sets of switching transistors. The interception device protects the switching circuit by preventing both transistor sets from entering the ON-state at the same time, and thereby prevent the switching means from breaking down.

Abstract: A motor driving device is provided with switches connected with both terminals of a motor in an H-bridge connection and malfunction detectors connected with both terminals of said motor. The malfunction detectors are comprised of an impression part and a detection part which can detect the breakdown of the respective switches caused by open breakage or short breakage according to an output signal from the detection part corresponding to an input signal from the impression part.