Although PoE power supply is more convenient, the use of more people, but estimated that a lot of people and I like, why its supply voltage is 48V and very confused, if you ask others, others will directly answer that is the industry standard of the PoE, then why would the provision for 48V? Focus on POE Switch equipment research and development of Fongrunda technology to explain briefly.
In fact, the early identification of PoE power supply standards, there have been arguments, the power supply voltage exactly set to how much more appropriate. Later, constant discussion and research, the voltage set at 48V, in the fluctuation is also possible, that is, the supply voltage between 44-57v. So why not 40V or 60V?
People who know about Poe's power know that it's done by cable, that is, the power signal and data signal in the network cable transmission to the other end of the device, if the power supply voltage is not enough, or the voltage is 40V, will cause the data signal transmission distance greatly decreased, perhaps only 30 meters, 40 meters. And since the use of Poe is certainly for the convenience of the hope of transmission farther away, so the supply voltage can not be too low.
Since then, it's a bit higher. 60V is good, it is estimated that some people believe that, indeed, the higher the voltage supply transmission must be the farther. But don't forget the network cable, how much it can withstand. The network cable will have current after power supply, the larger the current, the greater the cable strength, if more than 2 A, there will be problems or dangers. Like the wire in our home, if the line itself is very small, but connected to the power of a very large electrical appliances, then the possibility of the storage of burnt wires. Return to the Poe power supply, the voltage naturally cannot be so big, take 48V to be more eclectic.