<Dd> Photodetectors and infrared lighting elements can support digital screens to detect hand motions and gestures with the aid of machine learning algorithms . </Dd> <P> Many modern motion detectors use combinations of different technologies . While combining multiple sensing technologies into one detector can help reduce false triggering, it does so at the expense of reduced detection probabilities and increased vulnerability . For example, many dual - tech sensors combine both a PIR sensor and a microwave sensor into one unit . For motion to be detected, both sensors must trip together . This lowers the probability of a false alarm since heat and light changes may trip the PIR but not the microwave, or moving tree branches may trigger the microwave but not the PIR . If an intruder is able to fool either the PIR or microwave, however, the sensor will not detect it . </P> <P> Often, PIR technology is paired with another model to maximize accuracy and reduce energy use . PIR draws less energy than emissive microwave detection, and so many sensors are calibrated so that when the PIR sensor is tripped, it activates a microwave sensor . If the latter also picks up an intruder, then the alarm is sounded . </P>

How wide is the beam emitted by the motion detector