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How the Poe power switch is powered by a network cable?
Aug 25, 2017

The PoE power supply switch is a switch that can provide network power for the remote terminal, including the network switch and PoE power supply. It is the more common power supply equipment in the PoE power supply system. The port supports output power of 15.4W. IEEE802.3af standard, the port supports output power up to 30W, in line with IEEE802.3at standard, through the network cable power supply for the standard POE terminal equipment power supply, eliminating the need for additional power wiring. In line with the IEEE802.3aT standard POE switch, the port output power can reach 15-60 W. Popular said, POE power supply switch is to support the network cable-powered switches, not only can achieve the normal switch data transmission function can also power the network terminal.

POE (Power Over Ethernet) refers to the existing Ethernet Cat.5 cabling infrastructure does not make any changes in the case, for some IP-based terminals (such as IP telephones, wireless LAN access point AP, network cameras, etc. ) While transmitting data signals, but also for such devices to provide DC power supply technology. POE technology can ensure the safety of existing structured cabling while ensuring the normal operation of existing networks, to minimize costs. POE is also known as a LAN-based power supply system (POL, PoweroverLAN) or active Ethernet (ActiveEthernet), and sometimes referred to simply as Ethernet power supply, which is the latest standard for transmitting data and electrical power using existing standard Ethernet transmission cables Standard specifications, and maintain compatibility with existing Ethernet systems and users. IEEE802.3af standard is based on the Ethernet power supply system POE new standards, it is based on IEEE802.3 to increase the direct power supply through the Internet cable related standards, is the extension of the existing Ethernet standard, is also the first on the international distribution of power standards.


POE Standard

The POE standard defines two methods for transporting DC to POE-compliant devices using an Ethernet transmission cable: a method called Mid-Span that uses an idle line that is not used in an Ethernet cable To transmit DC, the corresponding EndpointPSE supports POE-enabled Ethernet switches, routers, hubs, or other network switching devices. Another method is the "End-Span" (End-Span), is the transmission of data used in the core line at the same time transmission of direct current, the transmission and Ethernet data using a different frequency. Mid-spanPSE is a specialized power management device that is usually put together with the switch. It corresponds to each port has two RJ45 jacks, one with a short-term connection to the switch, the other connected to the remote device. It is foreseeable that End-Span will be quickly promoted, because Ethernet data and transmission using a public line, thus eliminating the need to set the independent transmission of the dedicated line, which is only 8-core cable and matching standard RJ -45 socket is particularly significant.


POE power supply work process


When the POE power supply terminal is arranged in a network, the POE power supply operation process is as follows:


Detection: Initially, the POE device outputs a very small voltage at the port until it detects that the cable terminal is connected to a receiving terminal that supports the IEEE 802.3af standard.


PD Device Classification: When a receiving device PD is detected, the POE device may classify the PD device and evaluate the power loss required by the PD device.


Start power supply: During a configurable time (typically less than 15μs), the PSE device begins to supply power from the low voltage to the PD device until a 48V DC power supply is provided.


Power supply: PD equipment to provide a stable and reliable 48V DC, PD equipment to meet the 15.4W without power consumption.


Power off: If the PD device is disconnected from the network, the PSE will quickly (typically within 300 to 400 ms) stop powering the PD and repeat the process to detect if the terminal of the cable is connected to the PD.


A complete POE system includes power supply equipment (PSE, Power Sourcing Equipment) and power receiving equipment (PD, Power Device) in two parts. The PSE device is a device that powers the Ethernet client device and is also the manager of the entire POE power over Ethernet process. The PD device is the PSE load that receives the power supply, that is, the client of the POE system.