Intermatic's Smart Guard Surge Protective Device (SPD) uses TPMOV (Thermally Protected Metal Oxide Varistor) technology to protect your home or lite commercial environment from surges in power supply, eliminating the potentially hazardous failure modes that are commonly associated with standard MOV technology. Type 1 applications include outdoor installations before service entrances and utility meter cabinets. Type 2 applications include installations after service entrances. Installation of an Intermatic Smart Guard Surge Protective Device (SPD) provides surge protection for your entire home and all of the expensive appliances and electronic equipment inside your home, such as computers, gaming setups, home theatres and other electronic equipment. Smart Guard uses replaceable IModule with LED lights that indicate when IModule needs replacing.