The evolving standards of PoE
(blogger@L-com.com)
The IEEE standards for providing PoE have been around for almost a decade now, but the actual technology to accomplish this is even older. The original concept was pretty simple: Category 5 cabling has eight conductors, but the standard really only used four of them. The low-voltage power could be run along the unused conductors to provide enough power for most simple devices. Through the use of an "injector" at one end and a "tap" at the other end, the power could travel along without noticeable problems with the data. Within a few years, manufacturers of many different types of IP equipment began implementing designs that would accept power directly from the cable, eliminating the need for a "tap". Next, manufacturers of the Ethernet switching equipment developed PoE Injector Hubs to directly inject the power into the cable, eliminating the need for an "injector". But there were three big problems:
