Power Over Ethernet is a revolutionary technology that integrates data, voice and power on top of standard Ethernet infrastructure. PoE provides new options for power distribution over standard twisted-pair cable. This technology is used to power IP telephones, wireless LAN access points, surveillance cameras as well as remote network switches and embedded computers where expensive or infeasible to supply separate power. Appliances receive power as well as data over existing CAT5 cabling. This is similar to POTS telephones which also receive power and analogue data over the same cable. Formally known as IEEE 802.3-2005, Power over Ethernet supplies 48 V over two or four of the available category 3/Category 5e cable. Phantom power techique is used to transmit data over the twisted-pairs so that 100-Base-T and 1000Base-T (Gigabit Ethernet) can be used.
In 2003 the IEEE approved Power over Ethernet as an international standard - IEEE802.3af opening up new approaches to installing appliances and computer systems.
In addition to the benefits of international standardisation, Power over Ethernet offers an economical and safe route to rapid flexible deployment of computing devices.
To add Power over Ethernet to your network, a device called a Mid-Span-Hub can be added to existing ethernet switches to inject 48V DC onto CAT5 cables. Alternatively new power sourcing hubs and switches can be installed and connected to the existing cabling. To ensure safety power is only applied to devices that identify themselves as Power Over Ethernet compliant - existing Ethernet devices continue to receive data only.
Major vendors of networking hardware provide a range of Power over Ethernet hubs and switches giving choice of functionality and supplier. In addition standard UPS technology can be applied to Power over Ethernet hubs and switches to provide power-fail operation to Power over Ethernet devices from a central point.
More information:
Wikipedia.org | IEEE Standards
DSP Design | 3COM | Cisco
