Patent ID: 8604724

Claim:
A variable speed switch for adjusting a rotational speed of an electric power tool, comprising: a trigger configured to be pulled by a user; a resistive plate; a brush that can be slid in a given direction with respect to the resistive plate by a pull operation of the trigger of the electric power tool; a main switch-circuit; a subsidiary switch-circuit; and a controller for controlling the rotational speed of the electric power tool, wherein: resistance of the resistive plate changes according to a sliding position of the brush with respect to the resistive plate; in the main switch-circuit, a signal voltage is outputted from a terminal of the brush when a reference voltage is applied between a terminal of a brush-sliding-start side in the resistive plate and a terminal of a brush-sliding-end side in the resistive plate; in the subsidiary switch-circuit, the terminal of the brush-sliding-end side in the resistive plate and a terminal of the brush are electrically connected when the trigger is pulled to a given position; and the controller is configured to apply the reference voltage and to control the rotational speed of the electric power tool according to the signal voltage outputted from the terminal of the brush.