Over Ethernet- Up to 51 W of power over a single cable by
utilizing all four pairs in the Category 5 cable
over Ethernet or PoE technology describes a system to pass
electrical power safely, along with data, on Ethernet cabling.
PoE provides both data and power connections in one cable,
so equipment doesn't require a separate cable for each need.
For equipment that does not already have a power or data
connection, PoE can be attractive when the power demand
is modest. For example, PoE is useful for IP telephones,
wireless LAN access points, cameras with pan tilt and zoom
(PTZ), and remote Ethernet switches. PoE can provide long
cable runs e.g., 100 meters (330 feet) and deliver 12 W
of galvanically isolated power. PoE-plus provides even more
IEEE standard for PoE requires category 5 cable or higher
for high power levels, but can operate with category 3 cable
if less power is required. Power is supplied in common mode
over two or more of the differential pairs of wires found
in the Ethernet cables and comes from a power supply within
a PoE-enabled networking device such as an Ethernet switch
or can be injected into a cable run with a midspan power
The original IEEE 802.3af-2003[PoE standard provides up
to 15.4 W of DC power (minimum 44 V DC and 350 mA to each
device. Only 12.95 W is assured to be available at the powered
device as some power is dissipated in the cable.
The updated IEEE 802.3at-2009 PoE standard also known as
PoE+ or PoE plus, provides up to 25.5 W of power. The 2009
standard prohibits a powered device from using all four
pairs for power. Up to 51 W of power over a single cable
can be achieved by utilizing all four pairs in the Category
Numerous non-standard schemes had been used prior to PoE
standardization to provide power over Ethernet cabling.
Some are still in active use.