GROZONE TEMP-1V Day & Night thermostatic fan speed control Automatically slows down or speeds up centrifugal fans to respect user selected temperature day and night set points. Enables a much tighter and precise temperature curve. When ON/OFF controls usually yields a variation over 5°F / 3°C, TV1 will yield a variation below 2°F / 1°C. 6 foot cord with temperature sensor precise to 2°F / 1°C. Can drive single phase 120 Vac induction motor type fans up to 750 Watts. Any forced ventilation rooms should be equipped with this type of control to promote faster and more vigorous growth.