Sentinel GPS CPPM-4i Fuzzy Logic Intelligent CO2 Controller for Greenhouses and Gardens Sentinel Intelligent CO2 Enrichment (S.I.C.E.) allows interfaced CO2 enrichment with Sentinel ICG series generators for unparalleled control. Sentinel True Fuzzy Logic gives the most precise compressed CO2 regulator enrichment available,and its large pixelated LCD display makes user programming intuitive and simplified. Time Clock control provides greater user flexibility and control vs. older photocell models Remote Sensor is 15 (5m) expandable up to 160 (50m) accommodating a wider range of growing environments. RoHS compliant construction for environmental friendliness.