Abstract: An event detection system with centralized signal processing and dynamically adjustable detection threshold includes a number of remotely located event detection units coupled to a single centralized signal processing unit. Each event detection unit provides an event detection signal to the centralized signal processing unit. At least one signal processor in the centralized signal processing unit compares the value of the event detection signal with a dynamically adjustable threshold value, and provides a first detection signal when the event detection signal exceeds the value of the dynamically adjustable threshold. A threshold generator compares the event detection signal and a predetermined offset value, and adjusts the value of the dynamically adjustable threshold as the event detection signal exceeds the offset value. The signal processor then provides a second event detection signal when the event detection signal exceeds the adjusted threshold value.

Abstract: A passive intrusion alarm system having an array of infrared sensing elements arranged and sampled so as to provide a two dimensional thermographic image of an intruder.

Abstract: A signal detection system with dynamically adjustable detection threshold includes a signal detection comparator having a dynamically adjustable threshold which adjusts the detection sensitivity of the comparator from a quiescent value to a value which is dependent upon the value of an event trigger signal, thus anticipating the amplitude of a second, confirming event trigger signal. Additionally, an alarm window timer activated by an event signal which exceeds the quiescent signal detection comparator threshold, assures that an alarm activator will be enabled only after a second, confirming event trigger signal exceeds the adjusted detector threshold, and which occurs during the active period of the alarm window timer.

Abstract: An apparatus and method for combining detection signals generated by intrusion detection systems to provide improved alarm integrity therefor. The apparatus and method have utility with mixed sensor technology and single sensor technology detection systems. In one embodiment, analog detection signals generated by system sensors are combined in an analog multiplier and the resulting decision signal is compared via a unipolar threshold comparator or a window comparator. In another embodiment, analog detection signals are amplitude limited prior to being combined in the analog multiplier. In a further embodiment, analog detection signals are subjected to average value processing such that the decision signal has a value equal to one-half of the sum of the sensor signals. In yet a further embodiment, analog dectection signals are amplitude limited prior to average value processing.

Abstract: An infrared detection system having a detector which includes elements of different sizes which are electrically selectable to change the operational range of the system without any change in the associated optical assembly. The detector elements can be of two or more element sizes, and various detector configurations can be employed such as single or dual detector configurations. To provide a constant signal amplitude for the different selected ranges, the gain of the detector circuitry can be adjusted accordingly to provide uniform signal amplitude irrespective of range setting.

Abstract: An improved passive infrared balanced detector is disclosed that reduces false alarm rates induced from random thermal activity and other causes of splitting of the field(s) of view of the balanced detector into distinct and independent regions. The detector includes balanced elements selectively shaped and arranged to provide common mode rejection within each of the regions into which the field(s) of view are subject to being split. The unbalance susceptibility of the novel detectors may be adapted to the particular requirements of the intended applications environment. The susceptibility for unbalance is materially reduced and therewith the alarm confidence level of the detectors is substantially improved.

Abstract: An alarm system uses an area sensor having a piezoelectric film sensitive to changes in pressure. A piezoelectric film with electrodes deposited on opposite surfaces of the film converts changes in mechanical pressure to electrical signals. A signal processor detects the electrical signals and generates an output signal in response. The electrodes could comprise single metalized sheets deposited on each surface. Alternatively, an array or pattern of individually operative electrodes could be provided. An array or pattern of electrodes enables the signal processor to determine the location, motion, and direction of motion of a force generating pressure changes on the piezoelectric film. The alarm system may include a threshold detector sensitive to the magnitude of pressure changes so that an output signal will not be generated unless the pressure change is sufficiently great. This invention is suitable as a floor covering for detecting an intruder walking over its surface.

Abstract: A passive analog equalizer is connected to the output of an infrared detector to provide increasing pyroelectric detector sensitivity with increasing target frequency in order to provide a detection sensitivity which is substantially flat over the target velocity range of interest. An interruptable modulator is connected to the equalized pyroelectric detector signal to shift its frequency upwardly in order to provide negligible drift, fast recovery from transients, and the ability to quickly shut down the modulator when a transient occurs. A transient detector is operative in response to transients in the pyroelectric detector output signal to provide a window during which the modulator is interrupted in order to prevent transient induced false alarms.