Unit the emitter and the receiver as one. In that case, it has advantages of easy and convenient installation as we as wonderful collimation for the optical pathAutomatic calibration to make sure one person can debug the device easilySelf-testing function to monitor the internal fault of the detectorAutomatic compensation for the factors of the receiving signals to avoid the influence of dust pollution, positional deviation and aging of transmitter tubesThe detector is designed for optical path, strong anti jamming capability, seal design and reliable anti-corrosion and water proof4 reflectors for 100 meter smoke detection