ABSTRACT
The occupancy detectors detect the presence of people (and sometimes animals) in a monitored area. The motion detectors respond only to moving objects. One of the major aggravations in detecting occupancy or intrusion is a false-positive detection. Ultrasonic waves are mechanical compressions and rarefaction of air covering the frequency range well beyond the capabilities of human ears, that is, over 20 kHz. The microwave detectors offer an attractive alternative to other detectors when it is required to cover large areas and to operate over an extended temperature range under the influence of strong interferences, such as wind, acoustic noise, fog, dust, and moisture. There are several possible sources of interferences that may cause spurious detections by the triboelectric detectors. By far, the most popular intrusion sensors are the optoelectronic motion detectors. An array of detecting elements (multiple pixels) may be placed in the focal plane of a wide-angle focusing mirror or lens.
