Proximity alarm system
First Claim
1. A proximity alarm system comprising, in combination:
- a transceiver station including signal receiver means, and circuit means for generating and transmitting a remote signal encoded with a first predetermined code;
timing control means for selectively enabling the circuit means to transmit the remote signal;
a repeater station spatially separated from the transceiver station, including means for receiving the remote signal, means operably responsive to initial reception of the received remote signal for generating a timing signal encoded with a second predetermined code and means for transmitting the timing signal for reception at the transceiver station in response to cessation of the received remote signal;
decoder means at each station for identifying and accepting an encoded received signal intended for its respective station; and
discriminator means for detecting a time delay between the remote and timing signals at the transceiver station and generating a time shift value in response thereto corresponding to the distance between stations.
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Accused Products
Abstract
The spatial separation of an object from a reference location is monitored utilizing a proximity alarm system which comprises a transceiver station mounted on the object and a repeater station at the reference location. Both stations function to generate and transmit an encoded rf signal in a half-duplex manner, with the transceiver station initiating the process. In one embodiment of the system, a phase delay is measured between a remote signal originating at the transceiver station and a corresponding decoded timing signal received from the repeater station. Correlation of the phase delay with a reference value ascertains the distance between the stations and an alarm at the transceiver station is actuated when the distance exceeds a predetermined value. A second embodiment of the system employs a clock driven counter that is stopped when a predetermined multiple of decoded timing signals is received at the transceiver station in response to iterative transmissions therefrom. The count value of the counter is read and correlated with a transit time reference value to ascertain the distance between stations. An alarm is actuated if the distance exceeds a predetermined maximum.
113 Citations
20 Claims
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1. A proximity alarm system comprising, in combination:
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a transceiver station including signal receiver means, and circuit means for generating and transmitting a remote signal encoded with a first predetermined code; timing control means for selectively enabling the circuit means to transmit the remote signal; a repeater station spatially separated from the transceiver station, including means for receiving the remote signal, means operably responsive to initial reception of the received remote signal for generating a timing signal encoded with a second predetermined code and means for transmitting the timing signal for reception at the transceiver station in response to cessation of the received remote signal; decoder means at each station for identifying and accepting an encoded received signal intended for its respective station; and discriminator means for detecting a time delay between the remote and timing signals at the transceiver station and generating a time shift value in response thereto corresponding to the distance between stations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for operating a proximity alarm system, comprising the steps of:
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generating a remote signal at a transceiver station and transmitting the signal therefrom to a remotely located repeater station; receiving the remote signal at the repeater station; generating a timing signal at the repeater station in response to initial reception of the received remote signal; transmitting the timing signal from the repeater station in response to cessation of the received remote signal; and detecting a time difference between the remote signal generated and the timing signal received at the transceiver station comparing the time difference with a reference value and actuating an alarm when a predetermined time difference is exceeded. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification