Power over Ethernet, also known as PoE, describes a system that lets Ethernet cables supply the power for network devices while simultaneously transmitting data in the normal way. This is achieved in two ways: 1) Alternative A: Power is transmitted on the data conductors by applying a common mode voltage to 112 each pair. 2) Alternative B: The twisted pairs in an Ethernet cable are divided into 2 groups. Two of the four twisted pairs are assigned to transmit data, and the other 2 are assigned to transmit power. This alternative is typically easier to troubleshoot should problems arise since the assigned wires can be isolated. PoE products can be mixed in a network with non-PoE, but non-PoE products cannot send or receive power.
To see the actual publication please follow the link above