An off-load changeover switch is a device used to switch electrical circuits from one source to another without having to turn off the power. It is commonly used to switch between two different power sources such as a generator and a mains electricity supply. The switch is designed so that when the main supply fails, it automatically switches over to the generator, allowing the power to continue uninterrupted. The switch can also be used to switch between multiple sources, such as solar and wind energy.