Capacitive article removal alarm
First Claim
1. An alarm system for indicating the removal of an article from a predetermined position comprising:
- (a) sensing circuit means including(i) two electrical conductors spaced from but adjacent each other and for positioning adjacent to the predetermined position to be occupied by at least one article when in use, and(ii) signal generating means responsive to the capacitance present between these conductors to provide a first output condition indicative of substantially constant capacitance present between these conductors due to the undisturbed presence of said at least one article and to provide a second output condition indicative of a change in capacitance value present due to the disturbance of said at least one article, and(b) alarm actuator means responsive to the output of said sensing circuit means to provide an alarm indication responsive to said second output condition of said sensing circuit means.
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Accused Products
Abstract
The alarm system comprises a sensing circuit 12 which includes two electrical conductors 10, 11 spaced from but adjacent each other and adjacent to the predetermined position to be occupied by at least one item when in use. The sensing circuit includes a signal generator responsive to the capacitance present between the two conductors to provide a first output condition indicative of a substantially constant capacitance value present between the electrodes due to the undisturbed presence of the item and to provide a second output condition indicative of a change in capacitance value due to the disturbance of the item or items present. The output of the sensing circuit is received by an alarm actuating circuit 13 which causes actuation of an alarm element when the output condition from the sensing circuit changes significantly to cause the actuating circuit to trigger due to the movement of the item from its predetermined position.
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Citations
5 Claims
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1. An alarm system for indicating the removal of an article from a predetermined position comprising:
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(a) sensing circuit means including (i) two electrical conductors spaced from but adjacent each other and for positioning adjacent to the predetermined position to be occupied by at least one article when in use, and (ii) signal generating means responsive to the capacitance present between these conductors to provide a first output condition indicative of substantially constant capacitance present between these conductors due to the undisturbed presence of said at least one article and to provide a second output condition indicative of a change in capacitance value present due to the disturbance of said at least one article, and (b) alarm actuator means responsive to the output of said sensing circuit means to provide an alarm indication responsive to said second output condition of said sensing circuit means. - View Dependent Claims (2, 3, 4)
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5. A method of detecting and indicating when an article as been removed from a predetermined position comprising:
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providing two electrical conductors spaced from but adjacent each other and adjacent the predetermined position to be occupied by at least one said article, sensing the capacitance present between these conductors to provide a first output condition indicative of substantially constant capacitance value present between the electrodes due to the undisturbed presence of said at least one article and to provide a second output condition when a change in capacitance value due to the disturbance of said at least one article occurs, and actuating an alarm indicator whenever a change in the output condition occurs.
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Specification