When an initial position of an enabling switch is given as a first position (301), a position of the enabling switch in which a movable member is most pressed is given as a third position (303), and a rising start position of a maximum rise of a load is given as a second position (302), the rising start position being between the first position (301) and the third position (303), a minor peak (341) of the load appears between the first position (301) and the second position (302). An ON switching position (311) is between a falling start position (323) of the minor peak (341) and the second position (302). A maximum load during the minor peak (341) is greater than or equal to the load in the ON switching position (311) and less than or equal to the load in an OFF switching position (312).