Power Over Ethernet Interoperability Guide

PoE Is an Intrabuilding Standard

PoE is essentially an intrabuilding standard. There are some confusing references in IEEE 802.3at to Environment A and Environment B:

In Section 33.4.1.1, titled “Electrical isolation environments,” and in Section 33.4.1.1.2:

There are two electrical power distribution environments to be considered that require different electrical isolation properties. They are as follows:

•  Environment A: When a LAN or LAN segment, with all its associated interconnected equipment, is entirely contained within a single low-voltage power distribution system and within a single building.

•  Environment B: When a LAN crosses the boundary between separate power distribution systems or the boundaries of a single building…. ...