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.
In a method of intrusion detection, the steps of: multiplexing into a receiver at a central location individual signals developed by vibrations sensed by individual ones of a plurality of seismic sensors in an array disposed in a monitored region within which intrusion by surface movement or tunneling is to be detected to obtain a scan of the seismic sensors in the array; automatically stopping the multiplexing scan on a first individual sensor having a received vibration signal exceeding a predetermined threshold value to indicate the location of an intrusion; and sequentially selecting the received signal developed on second and third seismic sensors in the vicinity of said first sensor to more precisely determine the location of the intrusion.
Claim 2
Dependent Claim
119 words
In a method of intrusion detection, the steps of: multiplexing into a receiver at a central location individual signals developed by vibrations sensed by individual ones of a plurality of seismic sensors in an array disposed in a monitored region within which intrusion by surface movement or tunneling is to be detected to obtain a scan of the seismic sensors in the array; automatically stopping the multiplexing scan on a first individual sensor having a received vibration signal exceeding a predetermined threshold value to indicate the location of an intrusion; and sequentially selecting the received signal developed on second and third seismic sensors in the vicinity of said first sensor to more precisely determine the location of the intrusion.
Claim 3
Dependent Claim
141 words
In an intrusion detection apparatus: a plurality of individual seismic sensor means for disposition in an array in a monitored region within which intrusion by surface movement or tunneling is to be detected for developing individual sensed vibrations picked up by the individual seismic sensor means; receiving means for disposition at a central location for receiving and detecting the signals developed by said seismic sensor means; multiplexing means for multiplexing the individual sensed vibration signals into said receiver means; means for automatically stopping the multiplexing scan on a first individual sensor means having a developed vibrational signal exceeding a predetermined threshold value to indicate the location of an intrusion; and means for sequentially selecting the received signal developed on second and third seismic sensors in the vicinity of said first sensor means to more precisely determine the location of the intrusion.
Claim 4
Dependent Claim
141 words
In an intrusion detection apparatus: a plurality of individual seismic sensor means for disposition in an array in a monitored region within which intrusion by surface movement or tunneling is to be detected for developing individual sensed vibrations picked up by the individual seismic sensor means; receiving means for disposition at a central location for receiving and detecting the signals developed by said seismic sensor means; multiplexing means for multiplexing the individual sensed vibration signals into said receiver means; means for automatically stopping the multiplexing scan on a first individual sensor means having a developed vibrational signal exceeding a predetermined threshold value to indicate the location of an intrusion; and means for sequentially selecting the received signal developed on second and third seismic sensors in the vicinity of said first sensor means to more precisely determine the location of the intrusion.