PURPOSE: To simplify the mount structure of a hook level and the assembling by providing a wall part close to a U-shaped notch of a rib.

CONSTITUTION: A flange 23d of a handset latch member 23 is screwed to a housing 20 by a screw 24 while a shaft 22b of a hook lever 22 is fitted to a notch 21a of a rib 21. When the member 23 is fixed, a rib 23c is engaged with a notch 22c and a wall part 23b is close to the U-shaped notch 21a of the rib 21 to be in press contact with a shaft 22b. Thus, the shaft 22b is escaped from the U-shaped notch 21a and limited by the wall 23b and the hook lever 22 is in the mount state. Moreover, a printed circuit board 31 with the hook switch 30 fitted thereto is screwed to the housing 20 by a screw 32 and the hook switch 30 is opposite to a main body 22a of the hook lever 22. Even when the hook lever 22 is strongly depressed, the hook switch 30 is not excessively depressed and the hook switch 30 is protected.