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.