Alarm apparatus for movable barrier members
First Claim
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1. An alarm apparatus for use with a frame member defining an opening and a movable barrier member in the opening which is movable relative to the frame member, said alarm apparatus comprising:
- switch means for mounting on one of said frame and barrier members, said switch means being switchable between a first operative state and a second operative state, and being normally in said first operative state;
actuating means for mounting on the other of said frame and barrier members, said actuating means switching said switch means to said second operative state when said actuating means is in a predetermined position relative to said switch means;
timing means responsive to said switch means being in said first operative state for greater than a predetermined period of time for generating an alarm condition signal; and
alarm generating means responsive to said alarm condition signal for generating an alarm whereby generation of an alarm is delayed for said predetermined period of time to prevent generation of false alarms as a result of minor movements of said barrier member relative to said frame member.
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Abstract
A normally-open magnetic reed switch is mounted on the bottom of a venetian blind or similar barrier and a magnet is mounted in the window sill to hold the switch closed when the barrier is in its normal position. When closed, the switch shorts a timing capacitor in an associated alarm circuit. If the switch moves away from the magnet (thus allowing the switch to open) long enough for the timing capacitor to charge, an alarm signal is produced. Thus an alarm will not be produced by trivial movements of the barrier.
46 Citations
10 Claims
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1. An alarm apparatus for use with a frame member defining an opening and a movable barrier member in the opening which is movable relative to the frame member, said alarm apparatus comprising:
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switch means for mounting on one of said frame and barrier members, said switch means being switchable between a first operative state and a second operative state, and being normally in said first operative state; actuating means for mounting on the other of said frame and barrier members, said actuating means switching said switch means to said second operative state when said actuating means is in a predetermined position relative to said switch means; timing means responsive to said switch means being in said first operative state for greater than a predetermined period of time for generating an alarm condition signal; and alarm generating means responsive to said alarm condition signal for generating an alarm whereby generation of an alarm is delayed for said predetermined period of time to prevent generation of false alarms as a result of minor movements of said barrier member relative to said frame member. - View Dependent Claims (2, 3, 4)
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5. A barrier member mountable for relative movement with respect to a frame member defining an opening, said barrier member having an alarm apparatus associated therewith, said barrier member comprising:
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a first member being supportable by said frame member in said opening; a barrier depending from and being supported by said first member, said barrier being freely movable with respect to said frame member; switch means mounted on a portion of said barrier which is movable relative to said frame member, said switch means being switchable between a first operative state and a second operative state, and being normally in said first operative state; actuating means for mounting on said frame member, said actuating means switching said switch means to said second operative state when said actuating means is in a predetermined position relative to said switch means; timing means responsive to said switch means being in said first position for greater than a predetermined period of time for generating an alarm condition signal; and alarm generating means responsive to said alarm condition signal for generating an alarm whereby generating of an alarm is delay for said predetermined period of time to prevent generation of false alarms as a result of minor movement of said barrier relative to said frame member. - View Dependent Claims (6, 7, 8)
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9. A method for detecting entry through an opening by an intruder, the opening including a barrier member supported therein and being freely movable relative to a frame member defining said opening, the method comprising the steps of:
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mounting a switch means on one of said frame and barrier members, said switch means being switchable between a first operative state and a second operative state and being normally in said first operative state; mounting an actuating means on the other of said frame and barrier members to be in a predetermined position relative to said switch means when said barrier member is supported without moving in said opening, said actuating means switching said switch means to said second operative state when said actuating means is in said predetermined position; detecting the operative state of said switch means; and generating an alarm when said switch means is in said first operative state for greater than a predetermined period of time whereby generation of an alarm is delayed for said predetermined period of time to prevent generation of false alarms as a result of minor movements in said barrier member relative to said frame member. - View Dependent Claims (10)
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Specification