What is PoE and How does PoE work?

What is PoE?

PoE (Power over Ethernet) is a technology that transmits power & data through network cables. It uses existing Ethernet to simultaneously transmit data and supply power to IP terminal devices (such as IP phones, WAPs, IP cameras, etc.) through network cables.



PoE technology can guarantee the normal operation of the existing network while ensuring the security of the existing structured wiring and minimizing the cost.



In short, it is the power supply of the network cable, that is, adds power to the network cable, and transmits data and power through the network cable at the same time, so as to realize dual use of one line.

How does PoE work?


PSE, Power Sourcing Equipment    

PD, Power Device


1. Detection: At the beginning, the PoE switch outputs a small voltage on the port until it detects that the connection of the cable terminal is a receiving end device that supports the IEEE802.3af standard.


2. Start power supply: During a start-up period (generally less than 15μs), the PoE switch starts to supply power to the PD device from a low voltage until it provides 48V DC power.


3. Power supply: Provide stable and reliable 48V DC power for PD equipment, satisfying the power consumption of PD equipment not exceeding 15.4W.


4. Power off: If the PD device is disconnected from the network, the POE switch will quickly (usually within 300-400ms) stop supplying power to the PD device, and repeat the detection process to detect whether the terminal of the cable is connected to the PD device .