Overview PoE

The existing Ethernet, with its basic structure of Cat.5 cabling unchanged, not only transmits data signals for IP-based terminals (such as IP phones, WLAN access points, and network cameras), but also provides the DC power supply for the devices. This technology is called Power over Ethernet (PoE). The PoE technology ensures not only the security of existing structured cabling but also normal operation of the existing network, greatly reducing the cost.

PoE is also called Power over LAN (PoL) or Active Ethernet. It is the latest standard specification for making use of existing standard Ethernet transmission cable to transmit data and provide power. It is compatible with the existing Ethernet systems and users. IEEE 802.3af and IEEE802.3at are the technical standards that PoE must comply with. IEEE802.3af is the basic standard of the PoE technology. It is based on the IEEE 802.3, and the standards related to direct power supply through network cables are added. It is an extension of the existing Ethernet standards. IEEE802.3at is an extension based on the IEEE802.3af.

According to the definition of the IEEE802.3af standard, a complete PoE power supply system consists of two types of devices: Power Sourcing Equipment (PSE) and Power Device (PD).

• PSE: It provides power to other devices.
• PD: Devices that receive power. The power of the devices is usually not large.