| 摘要 |
A frame member having two side walls and two end walls surround a cavity, and a cylindrical member is supported for pivoting in the cavity of the frame member. A magnet is mounted on a side of the cylindrical member, and at least one magnetic switch is mounted on a side wall of the frame adjacent to the magnet. When the cylindrical member pivots beyond the predetermined angle, the magnetic switch will be actuated.
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