Power Over Ethernet (PoE) technology describes any system that transmits electrical power, in addition to data, to remote devices over standard twisted-pair wire in an Ethernet network. This technology is useful for powering network devices where it would be inconvenient or infeasible to supply power separately. Such devices include IP telephones, wireless LAN access points, IP cameras, IP sensors and instruments in industry, IP radios, digital clocks, and more. The technology is comparable to POTS telephones, which also receive power and data (although analog) through the same cable.
PoE works without requiring modification to the existing Ethernet copper cabling infrastructure. Power over Ethernet is standardized in IEEE 802.3af. The IEEE 802.3af-compliant power sources supply 48 volts DC to devices at a maximum current of 350 mA. This allows devices to draw up to 15.4 watts.The new IEEE 802.3at (PoE+) standard raises the wattage to 25.5 watts.