Seismic intrusion detector system
First Claim
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1. A surveillance system for monitoring man-associated seismic movements within a control area, comprising:
- means for generating an electrical signal responsive to seismic movement of the generating means;
a bandpass amplifier coupled to said generating means and having a bandpass between about 10 and 40 Hz to permit electrical signals representative of man-associated movements to pass;
threshold detector means for sensing signals from said bandpass amplifier exceeding a preselected voltage level greater than signals generated within said area by normal background noise within the bandpass range and for generating a pulse coicident with the first cycle of the seismic signal each time said voltage level is exceeded;
inhibitor circuit means for generating pulses responsive to said detector means output pulses separated by more than a given time period;
precounter means responsive to said trigger pulses for generating a resultant pulse when a preselected number of trigger pulses have been counted representing each man-associated intrusion into said control area;
counter means for counting said resultant pulses and for generating a volage proportional to the total count in said counter means;
normally disabled variable frequency oscillator means for generating an audio frequency signal proportional to the amplitude of said counter voltage;
means for enabling said oscillator means and for monitoring the resulting audio frequency signal to determine the number of man-associated seismic movements within said area.
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Abstract
A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.
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Citations
8 Claims
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1. A surveillance system for monitoring man-associated seismic movements within a control area, comprising:
- means for generating an electrical signal responsive to seismic movement of the generating means;
a bandpass amplifier coupled to said generating means and having a bandpass between about 10 and 40 Hz to permit electrical signals representative of man-associated movements to pass;
threshold detector means for sensing signals from said bandpass amplifier exceeding a preselected voltage level greater than signals generated within said area by normal background noise within the bandpass range and for generating a pulse coicident with the first cycle of the seismic signal each time said voltage level is exceeded;
inhibitor circuit means for generating pulses responsive to said detector means output pulses separated by more than a given time period;
precounter means responsive to said trigger pulses for generating a resultant pulse when a preselected number of trigger pulses have been counted representing each man-associated intrusion into said control area;
counter means for counting said resultant pulses and for generating a volage proportional to the total count in said counter means;
normally disabled variable frequency oscillator means for generating an audio frequency signal proportional to the amplitude of said counter voltage;
means for enabling said oscillator means and for monitoring the resulting audio frequency signal to determine the number of man-associated seismic movements within said area. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- means for generating an electrical signal responsive to seismic movement of the generating means;
Specification