Schneider Electric's Square D heavy duty safety switch is designed to be tough, reliable and provide exceptional performance in the most grueling conditions. All heavy duty safety switches feature a quick-make, quick-break operating mechanism, a dual cover interlock, and a color coded indicator handle. They also come with many field installable or factory installed accessories. This electrical interlock for switches rated 400A to 1200A comes in kit form for field installation. A pivot arm operates from switch mechanism, breaking the control circuit before the main switch blades break. Each kit contains instructions for proper field mounting. It is UL listed.