Atlas 1 CO2 Monitor/Controller comes with a 25 foot remote sensor. It features adjustable set point and elevation levels, a built in 'self calibration' function and an integrated photocell that enables operation in daytime hours only, when the plants need CO2. Simple to use and easy to operate. 15 Amps/120 Volt/60 Hz. Replacement sensor can be purchased separately. The sensor comes factory calibrated for precise CO2 readings and utilizes low voltage technology to avoid Radio Frequency Interference (RFI) from electronic ballasts.