Abstract: A motor control circuit for controlling supply of electric power from a power source to an electric motor, in particular for use in electric power tools, comprising: an output power device for controlling supply of current to the motor according to a duty ratio of a control input signal supplied thereto; current detecting means for detecting an amplitude of an electric current supplied to the electric motor; and feedback means for supplying the control input signal to the output power device, the duty ratio of the input control signal being increased with an increase in the electric current supplied to the electric motor as detected by the current detecting means. Since the torque otuput of the motor is increased when such a need arises, the need for more a complex and expensive continually variable speed control system is eliminated.

Abstract: A combined locking mechanism and switch especially for power tools has a switch, an actuator for directly turning on or off the switch, a locking member shiftable between a first position in which it is disposed in opposed relation to the actuator and a second position in which it is spaced apart form the actuator, and an actuating member for actuating the actuator through the locking member only when the locking member is placed in the first position.