|[PROBLEM] To ground an operation knob without touching a plate spring to the operation knob. |
[Solution] A DAP 1 includes a volume knob 3 made by a metal that has an operation tab 4 and a rotary axis 5 that extends vertically against the operation tab 4 and a discharged section 9e made by a metal that is separate against and opposed to a tip of the rotary axis 5 among predetermined distance in the axial direction of the rotary axis 5. The corner part of the tip of the rotary axis 5 is tapered toward the operation tab 4. Further, a protruding section 9f that projects toward the tip of the rotary axis 5 is provided in the discharged section 9e.