It was just a few years back that the rule of thumb for Network designers was to not locate the Data cables anywhere near the Electrical cables for fear of cross-talk, interference and corruption of the Data traffic. Now along comes Power over Ethernet Technology and all of a sudden not only is it OK to mix Data and Electrical cables but the Electricity for powering some Network devices is now actually INSIDE the Data cable. How did this happen? Who figured it out? How does it work? How can the new PoE Technology be used in Networks today and what about the future of PoE? Here some answers for these important questions.

Like most good Solutions, Power over Ethernet Technology started out as a problem. The problem was occurring with early implementations of Voice over Internet Protocol (VoIP) phone systems. Now traditional Phone sets take their power (48vDC) over the phone lines from the Central Office. With VoIP Phone systems, there was no Central Office, only the Customer's premise Network. Providing phone power with wall adapters proved unreliable and if building power was lost, the phones stopped working. To give proper credit, the first successful design and implementation of a proprietary PoE system was accomplished by Cisco in 2000. Their technique of putting 48v DC on the LAN Data cable along with the Data traffic helped them overcome Customer's objections to wall adapter powering and sell a lot of VoIP Phone systems.

The Buzz over PoE Technology really got going in 2001 and 2002 as other Manufacturers began taking advantage of this new powering technique. Soon other IP Phone Vendors and Wireless Access Point (Antenna) makers, who also had trouble with local 110v powering, also jumped onboard. At this point the IEEE 802.3 Ethernet Committee assigned PoE Technology to a working subcommittee and named it 802.3af. Getting a Standardized version of the Technology would be crucial so that any Manufacturer who wanted to could make their products PoE ready. The IEEE working group took commentary from 2001 to 2003 and by June 2003 they released the ratified IEEE 802.3af PoE Standard. Here's what they defined.

The two types of PoE Equipment defined were the Power Sourcing Equipment (PSE) and the Powered Device (PD). Power Sourcing Equipment would send the power out over the LAN cabling system to the Powered Device, which would be capable of taking it off the LAN cable, through the RJ45, and using it to power itself. The PSE would send out a maximum of 15.4 watts per link, which would be limited to standard Ethernet distances. Powered Devices are Network devices like VoIP Phones, Wireless Access Points and certain IP Security Cameras. The PD would take power from the standard RJ45 connector. More PoE ready Powered Devices are available to the marketplace in each subsequent year as Manufacturers learn that "PoE Ready" is a feature that helps them sell a lot more devices. PoE ready End devices reduce installation costs by as much as 90% over traditional powering techniques.

Power Sourcing Equipment is defined by the IEEE in two equivalent ways. It can be implemented as Endspan which is an Ethernet Switch with Powered Ports (a PoE enabled Switch) or as Midspan which is a Power Hub that is used along with a non-powered Switch the End User already has in place on their Network. Powered Devices can receive PoE equally well from either type of PSE per the IEEE Standard. The decision to use a Powered Switch or a Midspan Hub is left up to the End User, as it should be, and is usually based upon Application and Budget. Endspan costs more to implement and works only for applications falling within the Standard. Midspan costs less to implement and works for both Standard and Non-Standard applications.

Please see the "Related Links" Menu in this section for several papers which explain the Pros and Cons of Endspan vs. Midspan PoE products. LAN Power Systems makes Midspan PoE products. There are times when Endspan is the right solution and there are times when Midspan is clearly a better solution for the particular PoE application. The important thing to understand is it does not matter to the End device which powering technique is being used.

Many new Powered Devices are appearing in the marketplace and many more are projected each year. The majority of applications driving PoE investment today are VoIP Phones, Wireless Access Points and IP-based Security Cameras. Among the newer PoE ready End devices on the market or coming soon are IP Paging Speaker Systems, POS Terminals, Door and Gate Security hardware, Public Information signs, Building Access and Temperature Control Systems, Stage Lighting, In-Flight Entertainment Systems and many others.

While the current Standard will remain in effect, there is work going on with the IEEE Committee to define a higher powered PoE Standard which would allow for approximately 30 watts to be delivered to the End Device. This would open up a whole new range of applications for Power over Ethernet. This next version of the Standard, referred to as "PoE Plus" and is an ongoing effort with no firm date yet as to when it may completed and ratified by the Committee.

So for now, enjoy the benefits that PoE Technology has brought to Networks everywhere. Centralized, secure, low-cost powering of Network End devices is perhaps the greatest enabling Technology to happen to Ethernet Networks in the last 10 years. End Users have already saved millions of dollars in installation costs by adopting PoE Technology. Thanks for reading this section and hopefully it was helpful.