“Power over Ethernet (PoE Testers) is a technology that enables low power (up to 25 watt) devices that are connected to 10BaseT, 100BaseT, and 1000BaseT networks to receive conditioned DC power through the network connection thereby eliminating the need for an AC or battery-based power. PoE Testers enabled networks consist of Power Sourcing Equipment (PSE's) that provide DC power and Powered Devices (PSE's) that are the consumer of DC power. End-Span PSE's provide both power and Ethernet switching/routing functions while Mid-Span PSE's add DC power to existing Ethernet links. Power is delivered in a common mode (e.g. via transformer center taps) using 2 of the 4 pairs within a Cat5 (or later version UTP) cable structure.

PoE Testers was governed by the IEEE 802.3af standard that has been replaced by 802.3at. Under 802.3af, all PSE's are required to furnish up to 15.4 Watts to PD's that may consume up to 12.95 Watts. Under 802.3at, PSE's and PD's are divided into power level categories and many PSE's are required to mutually communicate PD power requirements via classification protocols.”