Square D™ Surgelogic™ EMD Surge Protective Devices (SPDs) are designed to provide high-quality surge mitigation for a wide variety of commercial, industrial or institutional indoor applications. The EMD designs are for standard or mission critical service entrance or distribution panel installations and include a disconnector switch as a standard feature. The EMD is a UL 1449 Type 1 listed device with optional UL 1283 listing for Type 2 option ("F" suffix).