The HP E610 External Power Supply (EPS) has two pairs of EPS ports (with four ports total). Each pair of EPSports can power up to 24 PoE ports with full 15.4 W Power over Ethernet (PoE) power, if only one of the EPS ports is used. Alternatively, each pair of EPS ports can simultaneously power up to 12 ports with full 15.4 W of PoE power on each of two switches if both EPS ports are used. Each pair of EPS ports can supply up to 408 W of PoE power. The 610 EPS also includes EPS power backup ports, which allow one 610 EPS with spare power to provide power backup for another 610 unit connected to it in a stack.