Early applications of PoE did not have standards and used idle power supply.
1. IEEE 802.3af
IEEE 802.3af (15.4W) became the first PoE power supply standard, defining the Ethernet power supply standard and becoming the mainstream implementation standard for PoE applications.
IEEE began developing this standard in 1999, with the earliest participating vendors including 3Com, Intel, PowerDsine, Nortel, Mitel, and National Semiconductor. However, the shortcomings of this standard have always constrained the expansion of the market. Until June 2003, IEEE approved 802 The 3af standard specifies power detection and control matters in remote systems, and specifies the way routers, switches, and hubs power IP phones, security systems, and wireless LAN access points through Ethernet cables. The development of IEEE 802.3af has included the efforts of many company experts, which has also enabled the standard to be tested in various aspects.
A typical Ethernet power supply system. Retain Ethernet switch equipment in the distribution cabinet and use a Midspan HUB with power supply to provide power to the twisted pair of the local area network. At the end of the twisted pair, this power supply is used to drive telephones, wireless access points, cameras, and other devices. To avoid power outages, a UPS can be selected.
2. IEEE 802.3at
IEEE802.3at (25.5W) was born in response to the demand for high-power terminals, providing greater power supply demand and meeting new demands on the basis of compatibility with 802.3af.
In order to comply with the IEEE 802.3af specification, the PoE power consumption on powered devices (PDs) is limited to 12.95W, which is sufficient for traditional IP phones and network cameras to meet the demand. However, with the emergence of high-power applications such as dual band access, video telephony, and PTZ video monitoring systems, the 13W power supply clearly cannot meet the demand, which limits the application range of Ethernet cable power supply. In order to overcome the limitations of PoE on power budgeting and promote it to new applications, IEEE has established a new task force aimed at exploring ways to improve the power limits of the international power standard.