The SHELECTROMARINE Power Supplies, besides the classic principle of operation of power supplies that convert the alternating stabilized voltage (AC) to the desired direct voltage (DC) load, are designed in such a way to have the advantage of receiving a second input with direct voltage (DC), so that in the absence of main power will automatically switch from AC/DC to DC/DC. This is needed in vessels where the use of a backup power source (batteries) is required apart from the main supply.