The OD850 Series TriTech detectors are for use outdoors and in other harsh environments. They use a combination of passive- infrared (PIR) and microwave detection with advanced signal processing.The detectors can distinguish between small, repetitive motions such as tree limbs moving in the wind and the more purposeful motions of intruders. These advanced processing techniques and the detectors' mechanical design combine to provide superior performance in a wide range of weather conditions.