What is Power over Ethernet?
Power over Ethernet (PoE) is a system that provides a constant supply of DC power to a computer network using the same Ethernet cables used for connectivity. Devices such as network cameras and IP telephones can hence be powered without the need for extra wiring. PoE is easy to maintain and requires little or no human intervention. Another name for PoE is Power over LAN (PoL).
-As defined by the IEEE 802.3af committee and ratified in June of 2003, Power over Ethernet (PoE) provides 48v DC over the unused pairs of Category 5 or better UTP LAN Data Cables. Ethernet Data signals continue to travel on wires 1,2,3 and 6. Power is either superimposed on the data wires (Endspan technique) or routed to the unused wires (wires 4,5,7 and 8 this is the Midspan technique). The End device to be powered picks the power off of its RJ45 connector and routes it into its power circuit. This eliminates the need for the End device to be powered locally from a 110v AC outlet. Up to 15.4 watts is provided to the End device per the 802.3af PoE Standard currently in place.
A Power over Ethernet system comprises of an Ethernet switch and a Power-Hub or a Power over Ethernet enabled Ethernet switch, which serves as the power source, and a number of Power enabled DTE, which are the loads. The system is a Star topology, where each load is connected with a dedicated connection to the centralized Power-Hub. The Power-Hub is connected in series to an Ethernet switch/Hub (cascaded) where the Power-Hub inputs are connected to the switch outputs, and the Power-Hub outputs are connected to the patch panel. Power is carried over the spare twisted pairs (pins 7 & 8) and (pins 4 & 5) in an ordinary Category 5 and above cable with negligible degradation of data communication.
Power over ethernet (PoE) is any technology that transmits power over an ethernet cable. Guidelines for standardization are set forth as the IEEE 802.3af protocol. 802.3af and power over ethernet are not necessarily the same thing, but in practice devices that conform to the standard will probably end up dominating the market. Power over ethernet is convenient whenever there is an ethernet cable available but plugging into a wall outlet is a hassle. Power over ethernet technology is threatened by the fact that ethernet cords are almost universally being phased out in favor of wireless networks. In the 802.3af standard, 48 volts of DC power are sent through the cable at a current of 350 mA to provide around 13 watts of power. Discussions in 2005 led to a new standard, 802.3at, that doubles the available power. Desktop computers in offices of the future may be powered by nothing but an Internet cable, eliminating the need for additional electrical wiring. Power over ethernet is also idea
Power Over Ethernet is a revolutionary technology that integrates data, voice and power on standard Ethernet infrastructure providing new options for power distribution. This allows IP telephones, wireless LAN access points, surveillance cameras and other embedded appliances to receive power as well as data over existing CAT5 cabling. Formally approved as an international standard, Power over Ethernet is established as an economical, safe power distribution method and is already deployed in corporations throughout the world.
