Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1981-01-28
1983-02-15
Swann, III, Glen R.
Communications: electrical
Condition responsive indicating system
Specific condition
340518, G08B 1300
Patent
active
043743781
ABSTRACT:
An intrusion monitoring system includes an array of seismic sensors, such as geophones, arranged along a perimeter to be monitored for unauthorized intrusion as by surface movement or tunnelling. Two wires lead from each sensor to a central monitoring station. The central monitoring station has three modes of operation. In a first mode of operation, the output of all of the seismic sensors is summed into a receiver for amplification and detection. When the amplitude of the summed signals exceeds a certain predetermined threshold value an alarm is sounded. In a second mode of operation, the individual output signals from the sensors are multiplexed into the receiver for sequentially interrogating each of the sensors. Again, if the output from any one of the sensors exceeds a certain predetermined threshold value, a stop pulse is generated which stops the multiplexer at that sensor. A third operating mode permits the operator to manually scan up and down the individual sensors in the vicinity of the output sensor which stopped the action of the multiplexer. In this manner a more precise location of the intrusion is obtained. An automatic gain control is provided for the receiver allowing the sensitivity of the receiver to be automatically adjusted for optimum sensitivity with changing background noise level.
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patent: 4233302 (1980-09-01), Hocking
Brekke D.
Manning J.
Swann III Glen R.
The United States of America as represented by the United States
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