The FSR SG-120HW Surge Supression Module can be installed in conjunction with the CB-12/CB-22/CB-224 series of ceiling boxes, or any other application where it is desired to provide surge protection of a single 15 AMP 120VAC branch circuit. It is a "Type 2 Surge Protective Device" used to protect branch circuits against damage from electrical transients occurring on the AC line. It provides protection against transients in all 3 modes; Line to Line, Line to Neutral, and Neutral to Ground. A diagnostic LED indicates ground presence, system power and that surge protection is active.