Definition: PoE

(Power Over Ethernet) Distributing power over an Ethernet cable (at least Cat 5) to a target device that is not plugged into an AC wall outlet. 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). In addition, PoE can be used as an electrical source for the most efficient LED lighting (see PoE lighting).

PoE sends electrical power over unused wires in eight-wire cables and over signal wires in four-wire cables. PoE networks are created with a PoE-based Ethernet switch, but PoE can also be added to a non-PoE switch. In addition, regular Ethernet devices can be used in a PoE network (see illustrations below). See Ethernet, IP phone, PoC and network camera.

          IEEE               Maximum
 Type     Standard           DC Watts

 PoE      802.3af-2003       15.4

 PoE+     802.3at-2009       25.5


          Linear Technology
          Proprietary

 LTPoE++  Four power levels  38.7, 52.7
                             70.0, 90.0

PoE Injector (Bottom Two Images)

Because so many regular non-PoE Ethernet switches are already in place, PoE injectors are commonly used to install a PoE access point.