h embodiment of the present invention, and are a plan view and a side view of an operating section which can be applied to the sixteenth or twenty-first embodiment; FIG. 211 is a partial sectional view of FIG. 209; FIG. 212 is a view showing an outer appearance of a knob shown in FIG. 211; FIG. 213 is an exploded view showing a groove formed at an outer periphery portion of the knob shown in FIG.