The Catalyst 4000 family of switches extends the Cisco Architecture for Voice, Video and Integrated Data (AVVID) networking capabilities of the Catalyst backbone to the enterprise wiring closet and branch office. The Catalyst 4000 inline power Fast Ethernet module enables the modular wiring closet infrastructure to provide centralized power for Cisco AVVID IP telephony networks. The module prepares the network infrastructure for IP-based converged business applications that will provide seamless communications and collaboration between branch and corporate sites.This Catalyst 4000 Auxiliary DC Power Shelf with two PSUs is a new auxiliary DC power shelf. To support the new demand for phone power on the Catalyst 4006, Cisco has developed a new auxiliary DC power shelf that supplies the Catalyst 4006 with the 48 volts needed for inline power.The auxiliary DC power shelf is a three-slot chassis that supports two or three auxiliary power-supply units (PSUs) that generate the 48 volts DC required for IP phones. Two PSUs are required in the non-redundant configuration as a minimum, supporting the full 240-port capacity of the Catalyst 4006. The third PSU is an optional fault-tolerant supply, providing N+1 redundancy.