This variable speed control utilizes full-wave phase control circuitry to minimize power loss reducing energy requirements while you control your variable speed fan. features: use for shaded pole, permanent split capacitor psc, and universal ac/dc motors built in on/off ac line switch minimum speed trimpot rfi noise suppression filter provides rfi and emi suppression flame retardant abs enclosure all models mount in a standard 2 x 4 electrical wall box ul & cul listed file# e51028 csa certified file# 030837_0_000