Power over Ethernet (PoE) is also called PoE power supply. It is a technology that can transmit power and data to devices through Ethernet over twisted pair.
Through this technology, devices such as VoIP, wireless base stations, cameras, hubs, and computers can be powered by PoE technology.
Wireless Access Points
Since electronic devices powered by Ethernet can be used without an additional power outlet, the time and money for configuring the power cord can be eliminated, and the cost of the entire equipment system is relatively reduced. RJ-45 sockets are widely used all over the world, that makes so all PoE devices are compatible. This technique is often compared to the traditional telephone network (POTS), which also receives power and data (although analog data) on the same cable. PoE does not need to change the Ethernet cable layout to operate, thus the PoE system not only saves cost, but also has the ability to control the power on and off remotely.
PoE power supply terminal is divided into Power Sourcing Equipment (referred PSE) and the receiving end (Powered Device, referred to as PD).
Power sourcing equipment (PSE) refers to devices such as a network switch that provides (sources) power on the Ethernet cable. When the device is a switch, it is commonly called an endspan. Otherwise, if it's an intermediary device between a non PoE capable switch and a PoE device, it's called a midspan. An external PoE injector is a midspan device.
Powered device (PD) refers to devices powered by a PSE and thus consuming energy. Examples include wireless access points, VoIP phones, and IP cameras.
Many powered devices have an auxiliary power connector for an optional, external, power supply. Depending on the PD design, some, none, or all power can be supplied from the auxiliary port, with the auxiliary port sometimes acting as backup power in case PoE-supplied power fails.