Hands are covered. When a moving object violates this invisible red line, the probe will detect the abnormality and give an alarm.
Infrared alarm can be divided into active type and passive type. Active infrared alarm is an alarm that actively emits infrared rays. When the infrared ray hits an obstacle, it will bounce back and be received by the probe of the alarm. If the probe detects that the infrared ray is still, that is, the red line is constantly emitting and bouncing, then the alarm will not give an alarm. When a moving object violates this invisible red line, the probe will detect the abnormality and give an alarm. The main materials of pyroelectric infrared sensor are lithium tantalate (LiTao3), triethyl sulfate (LATGS) and lead zirconate titanate (PZT).