| 摘要 |
A security screen includes a rectangular frame including a top member containing a screen reel comprising a rotatable core with a length of electrically non-conductive screen material affixed thereto. The screen contains parallel electrical conductors therein running lengthwise, and transverse conductors interconnect selected pairs of the lengthwise conductors to form therewith a single continuous electrical path which is interrupted if the screen is cut. A latchable drawbar is affixed along the lower edge of the screen, so that the screen can be drawn closed, against the bias provided by two torsion springs. One end of each spring is connected to the reel's core; its other end is attached to a stationary stub shaft, which serves as a terminal for connection to an alarm. The springs are electrically joined to opposite ends of the screen's conductor path, thus serving as non-sliding rotary electrical joints.
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