The use of microcontrollers in passive infrared detectors enables the application of optimal algorithms to detect a moving person. The PATROL-401PET and PATROL-901 digital PIR detectors apply the latest and most effective method of bipolar detection.

The algorithm, based on bipolar detection, includes an analysis of signals and a calculation of bipolar pulses within certain time intervals and allows the detector to be adapted to various objects with complex operational conditions.

In small premises with a stable climate - such as apartments, small offices or small shops - it is advisable to detect a person by using one monopolar or two bipolar pulses. In large premises with a varying environment, such as industrial plants, malls, supermarkets, warehouses or hangars, where the detector is subject to more severe conditions it is more effective to use a bipolar algorithm, based on 3 or 4 pulses.

The principle of bipolar detection has led to a detector with high interference immunity, which ignores disturbances, such as light exposure, sudden temperature changes, radio frequency interference (RFI) and electromagnetic interference (EMI). 

The PATROL-401 and PATROL-901 PIR detectors, which are based on bipolar pulse detection, detect successfully a person's movement in spite of the various interferences commonly found in large premises and virtually eliminate false alarms and costly service calls.