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Definition: PoE

(Power Over Ethernet) Distributing power over an Ethernet network. PoE enables remote network devices such as ceiling-mounted access points and surveillance cameras to be installed far away from AC power sources. PoE also eliminates the bulky AC adapter for each device (see wall wart), and it is used for efficient LED lighting (see PoE lighting).

A PoE switch creates a PoE network, which supports both PoE and Ethernet devices. With injectors, PoE devices can be added to an existing Ethernet network (see illustrations below). Using at least Cat 5 cable, electricity is transmitted over unused wires in eight-wire cables and over signal wires in four-wire cables. See Ethernet, PoC and network camera.
            IEEE               Maximum
 Type       Standard           DC Watts

 PoE        802.3af-2003       15.4

 High Power over Ethernet
 HPoE/PoE+  802.3at-2009       25.5

 Linear Technology PoE
 See LTPoE++.                  90.0

PoE Injector
When AC power is not available in remote areas, a PoE access point or camera is easily added to a regular Ethernet network with an injector.