A modular electrical automatic changeover switch (main switch) is an electrical device that automatically switches between two or more power sources in the event of a power outage or failure. It is designed to ensure uninterrupted power supply to critical loads such as lighting, communication systems, security systems, and other essential appliances.

A modular electrical automatic changeover switch works by monitoring the power supply from the primary source and switching to the backup source automatically in the event of a power outage or failure. The switch is programmed to detect changes in voltage, frequency, or any other electrical parameter that may indicate a power failure.

Once a power outage is detected, the switch automatically switches to the backup power source, which may be a generator, an inverter, or any other alternative power source. Once the primary power source is restored, the switch automatically switches back to the primary source and disconnects the backup power source.