A bushing has a hole being of a circular cross section and extending through walls of the bushing. The hole in the bushing has an upper portion forming a small-diameter portion and a lower portion forming a large-diameter portion. An operation shaft extends through the hole in the bushing. The operation shaft has an upper portion forming a small-diameter portion and a lower portion forming a large-diameter portion. The operation shaft is rotatable circumferentially relative to the bushing, and is movable axially relative to the bushing. The small-diameter portion of the operation shaft extends upward from the small-diameter portion of the hole in the bushing, and the large-diameter portion of the operation shaft is greater in diameter than the small-diameter portion of the hole in the bushing. A rotary component portion includes a rotatable member. The rotatable member is coupled to a lower portion of the operation shaft. The rotatable member is allowed to rotate together with the operation shaft and to be stationary independent of axial movement of the operation shaft. A first contact is fixed to a lower surface of the rotatable member. A second contact is resilient, and is provided on a fixed base plate. The second contact relatively slides on the first contact as the rotatable member rotates. A push switch portion is located below the rotary component portion, and engages a lower end of the operation shaft. The push switch portion operates when being pressed by the lower end of the operation shaft in accordance with axial movement of the operation shaft.