The 6000W ACV power supply features combined Mode Power Resiliency as an extension of the traditional combined mode power-supply behavior. Each power supply contains two smaller power supplies (called sub-units) . In Combined Mode Power Resiliency the system relies only on power from three out of four power-supply sub-units. Cisco 6000W Redundant Power Supply is one of many Redundant Power Supplies available through Office Depot. Made by Cisco.