In general, the number of devices that a POE switch can access will be affected by several factors, including the power supply standard of the POE switch, the total power supply of the POE ethernet switch and the transmission data and power required by the access equipment. The power supply standard of POE switch on the market mainly covers two kinds, one is IEEE802.3af and the other is IEEE802.3at. They define that the maximum power supply of POE switches per port is 15.4W and 30W, but due to a certain loss in the transmission process, the actual power supply for each port of the switch is only 12.95W and 25W. The above condition also determines that the power of POE ethernet switch of two standards cannot exceed 12.95W and 25W per port. Of course, a POE power switch of no matter which standard is self-adaptive, that is, how much the power of the access device is, then how much power the switch will supply. The total power supply power of a POE switch is, of course, related to the per port power supply rate of the switch, which is affected by the standard of the switch and the number of the switch interfaces. For example, the total power supply rate of the 24 port POE switch with the maximum per port power supply rate of 15.4W is about 370W (≈24*15.4), while the total power supply rate of the24 port IEEE802.3at standard POE switch with the largest power supply rate of 30W is about 720W (≈24*30W). The required transmission data and power of access devices are different due to different categories, application standards and so on, which will cause different transmission data and power required by them.