An Active Infrared Detector always consists of one transmitter and at least two receiver chips with high-quality optical systems. The scanning range is set by means of a mechanical micro-speed unit by changing the angle between the transmitter and receiver. This optical procedure is called triangulation or optical differential measurement.
Active Infrared Detectors are static—they only detect persons and objects if they break the beam. The detection area consists of spots, and depends to a large extent, on the optical center-to- center distances of the transmitter and receiver lenses. Several beams can be combined in a modular system to form a larger area.