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Definition: PoE

(Power Over Ethernet) Distributing power over an Ethernet network. Because the power and signal are on the same cable, PoE enables remote network devices such as ceiling-mounted access points, surveillance cameras and LED lighting to be installed far away from AC power sources. See PoE lighting and PoE switch.

A PoE switch creates a PoE network, which supports both PoE and regular non-Poe devices. With adapters, 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, LTPoE++, PoC and network camera.

Active vs. Passive PoE
Active PoE ports comply with IEEE standards and sense the power requirements of the target device. If older devices are not compliant, no current is delivered. In contrast, passive PoE switches send 24 volts without checking, forcing technicians to know the electrical requirements of the units they are installing.

                     IEEE     Max Power
 Class       Type  Standard    (Watts)

 1 PoE         1   802.3af      15.4
 2 PoE         1   802.3af       4.0
 3 PoE         1   802.3af       7.0

 4 PoE+        2   802.3at      30.0

 5 PoE++/UPoE  3   802.3bt      45.0
 6 PoE++/UPoE  3   802.3bt      60.0

 7 4PPoE       4   803.3bt      75.0
 8 4PPoE       4   803.3bt      90.0

PoE Injectors Add PoE to a Line
A PoE access point or camera is easily added to a regular Ethernet network with an injector, also called an "adapter."

Industrial-Class PoE Switch
This 8-port PoE switch from Omnitron Systems is a far cry from the common variety. It supports 10 Gigabit Ethernet as well as optical fibers (two SFP+ transceivers are plugged into the 10 Gbe ports). The switch accepts 12 to 57 volts of DC (top) and sends the exact amount of power required by the receiving device or none if not PoE enabled. If a connected device fails, that port can be remotely powered down. The DIP switches are used to configure the many options. See SFP.