644W Redundant Power Supply unit can supply 600 Watts of backup power to four switches in the event of an AC loss or failure of an internal power supply. Thermal overload protection prevents the RPU from overheating if a thermal overload occurs. Over-voltage protection shuts down an output channel if the voltage exceeds a preset threshold whereas over-current protection shuts down the RPU if the output load exceeds a preset threshold. Short-circuit protection prevents the RPU from being damaged from a short circuit on any output channel. It can be mounted in a standard 19" equipment rack(brackets included) or on a flat surface.