Details: The Generac RTSD100A3 100-Amp 120-240-Volt Single Phase Nexus Automatic Transfer Switch, Rated NEMA 3R, 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. The Generac RTSD100A3 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. Generac manufactures the widest range of power products in the marketplace including portable, residential, commercial and industrial generators.