Abstract: A passive infra-red detector including at least three sub-detectors, each sub-detector being operative to receive infra-red radiation from a corresponding one of at least three sub fields-of-view, each sub field-of-view being exclusively defined by an optical element which does not define any other sub field of view, the sub fields-of-view being angled with respect to each other, adjacent ones of the sub fields-of-view being separated by a gap of no more than 30 degrees and at least one of the sub fields-of-view having at least one of the following characteristics: extending over no more then 45 degrees in azimuth; and including not more than three azimuthally distributed detection zones, and signal processing circuitry, operative to receive output signals from the sub detectors and to provide a motion detection output.

Abstract: An intrusion detector for supervising a region including a sensor which views a plurality of fields-of-view of the region and provides an output responsive to motion of an infrared radiation source between the fields-of-view, a first filter which provides a first filtered output based on a first, predetermined, detection pulse frequency range of the sensor output, a second filter which provides a second filtered output based on a second, predetermined, detection pulse frequency range of the sensor output and processing circuitry which receives the first and second filtered outputs and detects, in either or both of the filtered outputs, a sequence of detection pulses indicating an intrusion condition.