| 摘要 |
A plurality of switches are arranged in a polygon on a printed circuit board and each of the switches is beneath or under a switch activating portion formed at the center of a pushbutton operation receiver portion. The pushbutton operation receiver portions are each supported over the corresponding switches through resilient arms that are integrally formed with a stay, which is secured to the printed circuit board at the center of the polygon. The pushbutton has a plurality of pushbutton operation transmission portions, each of which conveys the pressing force to the facing ends of the adjacent pushbutton operation receiver portions. When the pushbutton is depressed at a point between two switches, the pushbutton operation transmission portion nearest the depression point is lowered, pushing down the facing ends of the adjacent pushbutton operation receiver portions. Since only one end of each of the two adjacent pushbutton operation receiver portions is pushed down, these pushbutton operation receiver portions are inclined but not lowered, so that the switch activting portion at the center of each pushbutton operation receiver portion is not lowered, leaving the corresponding switches inactivated. in this way no two or more switches can be operated simultaneously.
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