Application Example -- Passive Infrared Detector for alarm system Tx ≈ 24576 x R10 x C6 ; Ti ≈ 24 x R9 x C7 。 (ref to schematic) R3 is a light dependent resistor which has low resistance under strong ambient light. This causes the detector to be operational only when the detection area is sufficiently dark. Document Outline High Performance PIR Motion Detector IC Symbol A Retrigerrable waveform(NOTE : VH=0.7Vdd, VL=0.3Vdd) Non-retriggerable waveform(NOTE : VH=0.7Vdd, VL=0.3Vdd)