The Generac RTSY2000A3 200-Amp 120-240-Volt Single Phase Nexus Automatic Transfer Switch comes with a service disconnect, rated NEMA 3R and works in tandem with the generator to monitor the utility power. When utility power is interrupted, the transfer switch automatically transfers power from the utility to the generator. When utility power returns, the transfer switch will return the electrical load from the generator back to utility. Use with Generac generators 25-60-Kilowatt for whole house or small business backup. The Generac RTSY200A3 is engineered with Generac's digital load management (DLM) technology, the Nexus Smart Switch is the smartest transfer switch on the market. It has the ability to cycle on and off two air conditioners without adding additional components, allowing for a smaller generator to cover more circuits than when paired with a standard transfer switch. The Generac RTSY200A3 200-Amp 120-240-Volt Single Phase Nexus Automatic Transfer Switch with Service Disconnect is UL, CUL listed, measures 6.3-Inch by 30-Inch by 13.5-Inch, weighs 39-pounds and comes with a 2-year limited warranty. Generac manufactures the widest range of power products in the marketplace including portable, RV, residential, commercial and industrial generators. At Generac, we protect the things that power your life by providing quality, affordable power solutions.