About this item Double Protection : Double protection of built-in mechanical interlocks and control circuits prevents two separate 120/240 volt AC power sources from entering the AC distribution board at the same time and causing a short circuit. This automatic transfer switch has a 30 second selectable delay with quick-connect terminals for easy installation. This transfer switch has been pre-wired to automatically change the primary source of AC current from shore power to generator or inverter power when activated Easy-to-remove protective cover with wiring schematic inside One Year Warranty is Provided. If you have any problem , please feel free to contact us. › See more product details