| 摘要 |
A coil is wound on a hollow plastic bobbin and mounted in a U-shaped ferromagnetic frame, there being a pair of aligned bosses on opposite sides of the bobbin bore at one end thereof fitting into cooperating slots in the frame. A ferromagnetic core is axially movable within the hollow bobbin and is urged away from the bottom of the frame by a leaf spring. A compact plastic housing covers the bobbin, coil, and the upper portion of the frame, and electric terminals, mounted in pockets at the top of the bobbin, project through slots in the housing to the exterior. Portions of the bobbin are extruded into openings in the base of the terminals to hold them in place, and a pair of tabs on the bobbin interact with slots in the housing, and posts on the inside corners of the housing form abutments to prevent over-insertion of the tabs in the slots. A hook on the bottom of the frame is shaped to be engageable with an opening in external support elements of differing thickness to facilitate installation. The coil contains a relatively fine gauge wire which acts as a fuse if the buzzer is energized beyond a predetermined time period.
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