Power over Ethernet (PoE) is a technology that transfers power over a physical Ethernet line. This article briefly discusses the mechanism for classifying POE devices.
On two pairs, through the midpoint of the transformer, "+" is supplied, on the other two "-" (voltage 52..57V for bt). This scheme minimizes the influence of the supply potential on the differential signal. The figure shows the standard bt, at and af use 2 pairs, not 4. The full voltage is not applied to the line immediately, since in general there is a possibility of burning an external device. First of all, the source (injector) and the receiver (splitter) must agree with each other (make a handshake). The handshake process is as follows (for example bt):
, , , POE . 25 . 10.1 . , . . , , , . , (14.5..20.5) . .
, (Event). 4 , . 5 8, . , / /, . , , . , . 53 ( 5, 6). 3 ( ), , . 4, . 5, . , , 5, , 4. , , .
After classification, the injector supplies (or does not supply) full voltage to the line. The standard introduces limits on inrush currents. Briefly, the third stage looks like this:
