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Ethernet CAT5 and CAT6 cables in their traditional role of transmitting high frequency data were missing a trick. It's electronically easy to separate DC from a high frequency signal, so why not use the existing wires to provide a DC potential at the other end of the cable? No mains power supply needed, ideal for cameras and many remote devices already connected via Ethernet cable. The 8 wires in the cable aren't very thick though and 100M is a long way. There's all sorts of specs to do with heating effect due to the resistance of the wires which need to be formally observed so the net result is two official standards, IEEE802.3af and IEEE802.3at, able to deliver 12.95W and 25.5W respectively at the PD.
There are a number of proprietary extensions to these specifications and some manufacturers don't use them at all. They may still offer the ability to transmit DC over the cables so it's still Power over Ethernet, just not necessarily compatible with the standards. Some products claim to be compatible with the 802.3at standard and offer up to 51 W by utilising all 8 wires in the cable, but strictly the 2009 standard prohibits the use of all 4 pairs in this way.
PSE / PD / Midspan
Generally there are 3 types of devices used in a PoE environment. A PSE, a PD and a Midspan. Poe functionality can be incorporated into most Ethernet devices. The PSE (Power Sourcing Equipment) is simply a specially configured power supply designed to provide power safely to a valid PD (Powered Device).
A simple handshake is used between the PSE and PD before power is allowed to flow from the PSE. The PSE is most often part of a switch or hub, or a variety of up/down converters which include an RJ45 connection and can usefully include a PoE facility. A Midspan is a type of PSE and in simple terms is typically a pass through RJ45 box which adds PoE power and acts as a PSE.
How Much Power?
Perversely, the relatively low powers that can be drawn through the thin wired cable are far more useful today because devices are becoming more energy efficient.
IEEE802.3af - maximum 12.95W at the PD.
IEEE802.3at - maximum 25.5W at the PD.
Stepping outside the standards brings a large increase in power for special applications, with jumps to 51W, 60W and beyond with the current max at 100W. Mention should also be made of the HDBaseT Alliance who have developed the HDBaseT specification aimed at multimedia and offering up to 100W of power via PoE.
Many higher power PSEs or midspans also include outputs that meet the lower power level standards.
The AG5200 PD module has a small package size that is ideal for applications such as IP Telephones, WiMAX access points, PTZ cameras and remote computer terminals
Silvertel's new Ag6100-HP PSE in conjunction with the Ag5500 PD module provides an end-to-end solution that delivers 60W over Cat5/6 cabling
Suitable for CAT5/6 cables, Silvertel's new 100W rated modules have been developed for the new generation of PoH/HDBaseT compliant products such as smart TVs, LCD displays, access control, etc
The PoLRE switches are designed specifically to handle any organization’s existing or future real-time voice requirements delivering a robust platform ensuring voice quality of service today and into the future. In addition to IP phones the PoLRE switch can support other IEEE 802.3af compliant devices such as IP cameras, speakers or wireless access points.
The Blackfly camera line combines Power over Ethernet, industry-leading affordability and a host of unique features for uncompromising value. Every Blackfly model comes packed with functionality designed to maximize performance and reliability
The controller is designed to fit into creative post production facilities, and includes attractive crystal look buttons that are designed for high reliability. The front panel can be removed to allow labeling of the customizable buttons. For world’s best illumination quality, all buttons are illuminated by both RGB and white LEDs so that a wider range of rich and clean colors can be displayed
Unlike most Ethernet switches, the environmentally hardened CNGE28FX4TX24MSPOE is designed for direct deployment in difficult out-of-plant or roadside operating environments. Featuring a low-profile 1-RU high rack-mountable package, these units may be mounted within any standard 19-inch rack cabinet, and the high-capacity power supply for operation of the switch and PoE PSE is completely self-contained
Optionally powered via PoE+ (IEEE802.3at) and similar to a DVR, the Aimetis E3200 requires no hard drive or software installation. And with no software activation required, the first camera is being recorded within minutes of unpacking the box
The RocketLinx ES7106-VB is an unmanaged Power over Ethernet Industrial switch with four IEEE 802.3af PoE ports, two Gigabit ports and 12/24VDC voltage boost
The Access 800® IP1 is an intelligent Power over Ethernet (PoE) solution that integrates all standard access control components – including ANSI/BHMA Grade 1 Corbin Russwin hardware, contactless reader, door status monitoring, and controller – into a single device.
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PoE is Green
If you haven't heard that we're all supposed to save energy then you really might be on a different planet. And PoE must continue to expand it's reach on this planet because of that imperative alone. Sending power down the same cable as data makes too much sense to ignore - versus the alternative of trailing wires, remote power supplies, power management and maintenance. Of course there are practical limits to the amount of power that can be provided in this way (long, thin cables provide those practical limits) but as devices continue to be built to use less power then PoE becomes increasingly more viable.