Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1995-04-28
1996-12-10
Swann, Glen
Communications: electrical
Condition responsive indicating system
Specific condition
340505, 340539, 342125, 342127, G08B 2100
Patent
active
055834884
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.
REFERENCES:
patent: 4804961 (1989-02-01), Hane
patent: 5021765 (1991-06-01), Morgan
patent: 5043702 (1991-08-01), Kuo
patent: 5402104 (1995-03-01), LaRosa
Sala Nicola R.
Sala Rocco L.
Sakovich Michael M.
Swann Glen
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