The HPE 640 Redundant/External Power Supply Shelf is used with the HPE 2920 Switch Series to provide redundant power to back up internal power supplies in the switches, as well as provide external power for applications where additional power is required, as in PoE+ applications. Unit ships ready to be populated with at least one optional power supply and power cable, purchased separately.Features Three modular power supply slots: Supports redundant power for up to eight HPE 2920 Switches: protects against internal switch power supply failures. Supports external power allowing up to three HPE 2920 48 Port PoE+ Switches to support 1440W of PoE+ power : allows all 48 ports of a PoE+ switch to offer 30W of PoE+ power at the same time. External redundant power supply: provides high reliability Easy configuration: provides full management features, available through connected HPE 2920 Switches Three power supply module slots: allows failure of a power supply in one bay to not affect the other two power supplies