A transfer switch is a device designed to take electrical load from multiple voltage sources. In home generator applications the transfer switch is designed to switch between the utility grid and a back up generator. When the utility grid is operating normally, the transfer switch powers the load from the grid. If the utility grid fails, the transfer switch connects the load to the back up generator until the utility grid comes back on line. While the load is powered by the generator it is isolated from the grid to protect the utility line workers who are assigned to fix the utility power grid.