3Com ProCurve E4500-48 - Page 25

Connecting a Redundant Power Supply to your Switch 4500 PWR 25
with the 3Com Power-over-Ethernet (PoE) network switches. In order to
meet the IEEE 802.3af (PoE) specification, the -48V output must be
isolated from earth (ground) and meet the isolation requirements in that
specification.