Intrusion detection system
First Claim
1. An intrusion detection system comprising:
- a line sensor responsive to magnetic and pressure disturbances and generating an output signal which is a function of such disturbances;
a first band-pass filter for receiving the signal generated by said line sensor and selecting and passing to its output portion of said signal within a first frequency range;
a second band-pass filter for receiving the signal generated by said line sensor and selecting and passing to its output the portion of said signal within a second frequency range;
means for generating a first threshold signal as a function of the signal at the output of said first band-pass filter;
means for generating a second threshold signal as a function of the number of zero crossings in the signal from said second band-pass filter;
means for comparing the signal from said second band-pass filter to said first threshold signal;
means for integrating the signal from said second band-pass filter when said signal exceeds said first threshold signal;
means for comparing the integral of said signal from said second band-pass filter to said second threshold signal; and
means for generating an alarm output when said integral of said signal from said second band-pass filter exceeds said second threshold signal.
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Abstract
A system for detecting intrusions into a protected area by personnel, vehicles, or other objects, including a sensor capable of detecting magnetic and/or pressure disturbances and a signal processing means for generating an alarm signal when an unwanted intrusion occurs. The signal processing apparatus includes a first band-pass filter for selecting the portion of the signal from the sensor which is within a first frequency range, and a second band-pass filter for selecting a portion of the signal within a second frequency range. Logic circuitry is provided to process the two analog signals from the two band-pass filters using amplitude, signal energy and zero-crossing characteristics of the two signals in a cross-channel relationship to eliminate false alarms which might be caused by disturbances such as lightning, thunder, or wind.
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Citations
7 Claims
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1. An intrusion detection system comprising:
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a line sensor responsive to magnetic and pressure disturbances and generating an output signal which is a function of such disturbances; a first band-pass filter for receiving the signal generated by said line sensor and selecting and passing to its output portion of said signal within a first frequency range; a second band-pass filter for receiving the signal generated by said line sensor and selecting and passing to its output the portion of said signal within a second frequency range; means for generating a first threshold signal as a function of the signal at the output of said first band-pass filter; means for generating a second threshold signal as a function of the number of zero crossings in the signal from said second band-pass filter; means for comparing the signal from said second band-pass filter to said first threshold signal; means for integrating the signal from said second band-pass filter when said signal exceeds said first threshold signal; means for comparing the integral of said signal from said second band-pass filter to said second threshold signal; and means for generating an alarm output when said integral of said signal from said second band-pass filter exceeds said second threshold signal.
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2. An intrusion detection system comprising:
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a line sensor responsive to magnetic and pressure disturbances and providing an output signal which is a function of such disturbances; means for generating a first analog signal which is a portion of the signal provided by said line sensor within a first frequency range; means for generating a second analog signal which is a portion of said signal provided by said line sensor within a second frequency range; means for generating a first control signal as a function of said first and second analog signals; means for generating a second control signal as a function of said first analog signal; means for generating a system control time window as a function of said first control signal; means for generating a zero crossing control time window as a function of said first and second control signals; means for detecting the zero crossings in said second analog signal; means for generating a detection threshold signal as a function of said zero crossings of said second analog signal, said system control time window, and said zero crossing control time window; means for integrating the portions of said second analog signal appearing within zero crossing control time windows in each system control time window; means for comparing the integral of said second analog signal to said detection threshold signal; and means for providing an alarm output signal whenever said integral of said second analog signal exceeds said detection threshold signal. - View Dependent Claims (3, 4, 5, 6, 7)
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Specification