The PPM-1c Monitor from C.A.P. is an add-on ppm CO2 controller that connects to either the CO2-2, CO2-4 or CGC-1. The timers built into the atmosphere controllers continue to coordinate with the PPM-1c to give you the precision control not possible with other manufacturers CO2 control systems using only ON/OFF control. You enter the level of CO2 you want to maintain (usually 1500 PPM) and youre done. Rated for 1/2 amp. 3 year no hassle warranty