Antitheft system
First Claim
1. An antitheft system comprising an alarm unit to be connected to an article to be prevented from being stolen, and a nullification device for transmitting a nullifying signal to the alarm unit, the alarm unit comprising alarm means for producing an alarm, detecting means for detecting disconnection of the alarm unit from the article to produce a detection signal, and alarm control means for operating the alarm means upon receiving the detection signal and nullifying the detection signal after receiving the nullifying signal from the nullification device, the nullification device comprising:
- means for generating the nullifying signal at all times in an operative mode or generating the nullifying signal in response to the user'"'"'s manipulation,activation commanding means for giving an activation command in response to the user'"'"'s manipulation,means for producing a variable increasing with lapse of time or with the frequency of the user'"'"'s manipulation for generating the nullifying signal,means for resetting the variable producing means in response to the user'"'"'s manipulation, andnullification control means for setting the nullifying signal generating means in the operative mode in response to the activation command while setting the nullifying signal generating means in an inoperative mode upon the variable produced by the variable producing means exceeding a predetermined threshold value.
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Accused Products
Abstract
A nullification device of the invention comprises a nullifying signal generator 15 for producing a nullifying signal, and a controller 14 for measuring a predetermined period of time and on/off-controlling a mode change switch 16 provided between the signal generator 15 and a transmitting antenna 18. On the other hand, an activation device comprises a generator 23 for producing an activating signal for the nullification device. The activation device and the nullification device have connection terminals a, b and a'"'"', b'"'"', respectively, where the devices are in contact with each other, with the nullification device placed in a accommodating recess in the activation device. The controller 14 turns on the switch 16 in response to the activating signal, starts to measure time upon cessation of supply of the activating signal, and turns off the switch 16 upon lapse of the specified time period, whereby the nullification device for forcibly ceasing the generation of an alarm by an alarm unit is prevented from being used wrongfully.
50 Citations
9 Claims
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1. An antitheft system comprising an alarm unit to be connected to an article to be prevented from being stolen, and a nullification device for transmitting a nullifying signal to the alarm unit, the alarm unit comprising alarm means for producing an alarm, detecting means for detecting disconnection of the alarm unit from the article to produce a detection signal, and alarm control means for operating the alarm means upon receiving the detection signal and nullifying the detection signal after receiving the nullifying signal from the nullification device, the nullification device comprising:
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means for generating the nullifying signal at all times in an operative mode or generating the nullifying signal in response to the user'"'"'s manipulation, activation commanding means for giving an activation command in response to the user'"'"'s manipulation, means for producing a variable increasing with lapse of time or with the frequency of the user'"'"'s manipulation for generating the nullifying signal, means for resetting the variable producing means in response to the user'"'"'s manipulation, and nullification control means for setting the nullifying signal generating means in the operative mode in response to the activation command while setting the nullifying signal generating means in an inoperative mode upon the variable produced by the variable producing means exceeding a predetermined threshold value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification