The STFV Plus Series combines Active Tracking filtration for low energy noise and surge protection for high energy transients. These devices protect your equipment by continuously tracking input AC power and responding instantly to high voltage transients and high frequency noise caused by everyday events such as turning on machinery, motors, or equipment. Theyre available as hardwired, single phase units in a wide range of amperage ratings to meet your requirements, and are designed for years of trouble free operation with little or no user intervention after installation.