An Automatic Transfer Switch, or ATS, is a critical part of an automatic power system. The ATS is connected to a panel, either a main or a subpanel, and must have a current rating equal to or larger than the panel to which it is installed (100 amp, 200 amp, etc).

The Automatic Transfer Switch will disconnect the elctrical panel from the utility and connect to the generator when needed, then reconnect to the utility when power is restored.