Power over Ethernet or PoE technology describes a system to pass electrical power safely, along with data, on Ethernet cabling.  The standard for PoE requires cat5 cable or higher for high power levels.  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 added with a midspan power supply and injector.

The 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.

Very recently, GigE Vision output machine vision cameras have become available with Power Over Ethernet (PoE) enabling single cable connection which is very convenient for some applications.