The operational principle of dual-element passive infrared detector is in terms of detecting humans infrared spectrum. When people move within detectors working range, human bodys infrared radiation will be focused through lens, accordingly received by thermal-release electron. Because two thermal-release electrons receive different heat, which cannot counteract, the detector will alarm after signal processing. It is widely applied to bank, warehouse, house and so on. It also has many functions, such as auto temperature compensation, anti light interference, prevent pets, anti high-frequency interruption and so on.