DFIR** determines alarms by requiring two differen-frequency signals from special detectors and optics. Non-moving stimuli cause two signals both at the same frequency; thus no false alarm. Moving persons generate two different signal frequencies – so DFIR determines a true alarm.
Ordinary PIR sensors determine alarms by only one signal from a simple infrared light detector. Non-moving stimuli can cause the same signal-DFIR?** sensors reject this kind of false alarm.
-Selectable processing sensitivity for different environmental requirements.
-Superior False Alarm Immunity