The VPB-260 is a fully filtered battery back-up power supply. The input and both outputs are fuse protected. The charger circuit output is floating with respect to ground. The charging circuit provides a constant voltage and current limited to 1.5 amps to the two Gel Cells. There is a "power on" LED that is illuminated when the supply is connected to the AC power source. There is also a test button for testing the batteries. When pressing the button, the LED will illuminate if the batteries are fully charged.