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Power over Ethernet (PoE)

By Mary E. Shacklett

What is Power over Ethernet?

Power over Ethernet (PoE) is a technology for implementing wired Ethernet local area networks (LANs) that enables the electrical current necessary for operating each device to be carried by Ethernet data cables instead of standard electrical power cords and wiring.

Used both in smart home applications and business premises, PoE uses cheaper Ethernet cabling, which can transport both power and data, instead of electrical wiring, which supplies power only and requires separate wiring for data. Because PoE transports both power and data over Ethernet cable, less wiring is necessary, and electrical wiring can remain intact.

The PoE standard was developed in 2003 to support devices like wireless access points (APs). Prior to that, individual vendors used various forms of proprietary PoE to provide PoE capabilities. Some of these proprietary PoE devices remain in use today. PoE installers must determine where these older, proprietary devices are located because they can prove to be troublesome or incompatible with the standard PoE devices that came later. Today's standard PoE devices make AP installations easier and more flexible, especially in ceilings, which can be difficult areas to wire for electrical power.

How does PoE work?

For PoE to work, the electrical current must go into an Ethernet data cable at the power supply end and come out at the device end. With Ethernet, the power current can be kept separate from the data signal so neither interferes with the other. Current enters the Ethernet cable via a component called an injector. If the device at the other end of the cable is PoE-compatible, it will function properly without modification. If it is not PoE-compatible, a component called a picker, or tap, must be installed to extract the current from the cable. This picked-off current is routed to the power jack.

What devices use PoE?

Equipment built to the 2003 PoE standard initially delivered enough power for most APs but could not provide enough power for other types of mounted technology, such as video surveillance cameras. Over the years, the Institute of Electrical and Electronics Engineers (IEEE) and several vendors have attempted to address the power issue, but interoperability problems have persisted.

POE supports the following devices that consume 30 watts (W) of power or less:

In 2018, IEEE released IEEE 802.3bt, a new PoE standard also known as high-power PoE or PoE+. It accommodates use of four-wire pairs with Cat5 or Cat6 cable, which supports individual devices that require as much as 90 to 100 W of power. Devices this standard supports include the following:

PoE benefits

The advantages of PoE include the following:

PoE drawbacks

PoE is not a panacea. Concerns can include the following:

Learn which IEEE 802 wireless standards apply to technologies such as Ethernet and wireless.

19 Aug 2021

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