The 2828.1 Speed Control Switch is 10 amps and 120 volts. It is for use with several S & P exhausters up to 1/2 HP. Installation of a control switch allows your exhauster to be controlled from the ventilated area. The solid state control is matched to the motor and blower wheel allowing for continuous reduction in performance. This allows adjustments of airflow for system balancing. CFM is reduced in direct proportion to motor speed reduction.