The H3C RPS 800-A Redundant Power System is an external DC power supply unit for the H3C S5500-52C-EI that uses AC input and provides DC output for switch redundant backup power. This redundant power system (RPS) provides selective DC outputs. Depending on the connected DC output cable (s) , the RPS can provide +12 V DC, -54 V DC, or +12 V DC and -54 V DC concurrently to the powered device. The RPS 800 supports cold backup of power supply, which means it only switches to the DC output state when it detects a power supply failure of the powered device. HP H3C RPS 800 Redundant Power Supply is one of many Redundant Power Supplies available through Office Depot. Made by HP.