APC's Rack Automatic Transfer Switch (ATS), also known as the Redundant Switch, is a high availability switch that has two input power cords, one for each AC line, which provide redundant power to connected equipment. The Rack ATS is designed to supply power to the connected load from a primary AC source. If that primary source becomes unavailable for whatever reason, the Rack ATS will automatically begin sourcing power from the secondary source. The transfer time from one source to the other is seamless to the connected equipment.