The old "power bricks" that supply the 1541-II/1571-II/1581 floppy disk drives lose their reliability over time and can then damage the drive through overvoltage. The 1541-II Power Guard is connected between the power supply and the floppy drive, it monitors the voltages on the 5V and 12V rails and immediately disconnects if an overvoltage occurs. It thus makes a valuable contribution to protecting your old hardware.