- The automatic changeover switch controller governs the all system. It is about a programmable controller that continuously monitor the power utility, the backup generator and the engine. - The Power utility (or mains if you will) is connected via protection FUSES to the automatic changeover controller. - The backup generator is connected via protection as well. This protect the cables in case of short circuit. - The Generator Auto Start Module takes care to start the engine. - The Changeover Switch is made of two contactors with embedded auxiliary contacts an interlock mechanism. - The auxiliary relays drive the coils of the contactors. - The auxiliary relays drive the Generator Auto Start module. - Power Utility (sometimes called ‘MAINS’) - The Generator Power Connections (usually 3-phase with neutral).