High Tech Talk

What is Power over Ethernet (PoE) ?

As the application of Power over Ethernet (PoE) technology is more convince than before and more devices support PoE PD technology; But the knowledge is not popular like as Ethernet, because the power Ethernet technology deliver DC power into the traditional Ethernet cable and also need recognize the device which linked on the end of cable whether is IEEE 802.3af PD or not. This document will illustrate the behaviors and wiring architecture of power over Ethernet technology between Power Sourcing Equipment (PSE) and Powered Device (PD).

Power over Ethernet Wiring Architecture

        End-point Architecture -- Alternative A, B

IEEE 802.3af specified the PSE feeding power to PD through Ethernet Cable Data pairs – Alternative A mode (RJ-45 conductors 1, 2, 3 and 6) or spare pairs- Alternative B mode (RJ-45 conductors 4, 5, 7 and 8) and there is no additional equipment is located between PSE Switch/Hub and Powered Device.

        Mid-span Architecture – Alternative B

Mid-span is also specified into the IEEE 802.3af standard, it is applied for that Switch/Hub without PSE function. There is one Power Insertion Equipment located between Switch/Hub and PD; Power feeding through the spare pairs – Alternative B mode (RJ-45 conductors 4, 5, 7 and 8)

Benefits

• Significantly decrease of installation costs in electricity cabling.
• Excellent flexibility in the locating of IP cameras, video servers
  and transcoders.
• Eliminates the chance of power fail when combined with a UPS to
  do central power managements.