POE power supply switches are powered by network lines. As we all know, ordinary network lines are made up of 8 tiny copper wires, and two are around together and there are 4 pairs of lines. According to the production standards of twisted pair lines (EIA/TIA 568A and EIA/TIA 568B), 1 and 2 must be guaranteed to be around together, 3, 6 around together, 4, 5 around, 7, 8 around.
But when transmitting data signals in 10M and 100M networks, only two of them (12, 36) are used, so the other two pairs of wires can be used to transmit electricity. There is also direct use of data line pairs to transmit power, and DC power and data are transmitted on the signal line pairs according to different frequencies, so the data and the DC power do not interfere with each other. The POE power supply switch standard allows the above two uses. When the idle foot is supplied, the 4 and 5 pins are connected to the positive electrode, and the 7 and 8 pins are connected to the negative pole. When the data foot is supplied, the DC power is added to the middle point of the transmission transformer without affecting the data transmission. In this way, the 1, 2, and line pairs 3 and 6 can be arbitrary polarity. DC power is generally 48V, the reason is that the 48V is due to the voltage drop on the network line, if the voltage is too small, to the end voltage may not be enough, resulting in the device can not start.
Using the 45 and 78 connection mode is called the middle span connection method, using the 12 and 36 connection mode is called the end span connection method. Gigabit network, because 8 lines are used to transmit data signals, so there is no so-called free foot and data foot, that is, the power supply of 45, 78, and 12, 36 mode power supply.
The standard POE power supply switch requires the process of detection - Classification - starting power supply - power supply - power interruption, whether it is intermediate or end - to - end connection. This is the standard to measure whether the POE is standard, because there is no detection and classification link, as long as the connection starts power supply, so there is a burning device. Yes, not recommended.