Precision dual wavelength sensor - Seperate sensor Precision dual wavelength sensor - Seperate sensor and controller - Sensors deployed in grow area while controller is in convenient viewing location. - Easy upgrade to dual sensor - Just plug in second sensor and controller automatically begins to use it. (Second sensor sold seperatly) - CO2 sensors incorportate light sensors to shut off CO2 control when lights are off. - CO2 sensors include tempature sensors with user settable alarms to shut off CO2 when temperature is exceeded. - One 6A fused relay with LED indication per sensor. 2nd relay becomes a ventilation contoller when one sensor is used. - Factory set for most popular settings and large easy to use keypad to change settings if needed. - Large 10mm high characters LCD.