Power over Ethernet Primer


Power over Ethernet (PoE) is a method of providing power to a network device using the same Ethernet network cable that delivers data to the device. The advantage to this is being able to power the device without having a separate electrical connection. The current standard is commonly known as “802.3af”, which was adopted by the Institute of Electrical and Electronics Engineers (IEEE) in 2003.

PoE devices are either devices that provide power or devices that require power. Devices that require power (known as Powered Devices) simply operate from the power provided on the network connection. Power providers (known as Power Sourcing Equipment) can be made available in two ways. The most common method of supplying power is with a Local Area Network (LAN) switch that has PoE capability built in. An alternative method of providing power is with a midspan injector, which supplies power to an existing data network. The midspan device is installed inline between the data switch and the endpoint device. The midspan device injects power onto the Ethernet connection without affecting the data.

The PoE specification includes details on how the Power Sourcing Equipment and the Powered Device work with each other. The specification defines five classes of power requirements, 0 through 4, with differing levels of power required by the Powered Device. All Valcom devices are compatible with IEEE 802.3af Class 3. The actual power used will vary, depending on the type of device and the activity of the device at any given time.