The active infrared spectrum should be in the visible spectrum, greater than 0.76um, our company's infrared spectrum wavelength is generally in 0.94um, the transmitter usually uses infrared light-emitting diode as the light source, its main advantages are small size, light weight, long life, AC and DC can be used, and can be directly driven by transistors and integrated circuits. Most of the current active infrared intrusion detectors use complementary self-excited multi-resonant circuit as the driving power supply, directly added at both ends of the infrared light-emitting diode, so that the pulse modulated infrared beam, high duty ratio, which not only reduces the power consumption, but also enhances the anti-interference ability of the active infrared intrusion detector. The photoelectric sensor in active infrared receiver usually adopts photodiode, phototriode, silicon photocell, silicon avalanche diode and so on.