The Knowledges of POE
Power over Ethernet is the ability to provide 48V DC power over the same Ethernet copper. Embodiment requires two major equipment PoE - power supply (the PSE), i.e. LAN or Ethernet switches on the power supply source, and a power device (the PD), i.e., received from the Ethernet cable and use power to operate the terminal device .
PoE advantages: In addition to providing universal power supply for the connected device support the Ethernet cable from the outside, PoE reduce capital expenditures, thereby reducing the total cost of deploying integrated into a unified IP infrastructure powered device. PoE eliminates the need to install wall power connections for end devices, thereby reducing the cost of power outlets associated with supporting end devices. It also provides greater flexibility in installing network-attached devices where the local AC power supply is more difficult to deploy.
PoE switches: PoE switches can also provide DC power for some IP-based terminals (wireless access point AP, VoIP phones and IP-based surveillance cameras) while transmitting data signals. Use a standard CAT5 cable can provide power for the wireless AP and IP cameras. Power over Ethernet (PoE) optimized Powered Device (Power Device) installation and power management, for many new network equipment to reduce the time and cost of installation.
PoE: Power over Ethernet (Power over Ethernet) is a local area network technology that provides DC power to the powered device via twisted pair and is now widely used in enterprise and industrial applications.
PSE: Power supply equipment The Power Sourcing Equipment, PSE device is a device that powers the Ethernet client device and is also the manager of the entire PoE Ethernet power supply process.
PD: Power device, PD Device is a PSE load that receives power, that is, many other Ethernet devices such as IP phones, network security cameras, APs and PDAs or mobile phone chargers, such as POE systems Network equipment (in fact, any power does not exceed 13W of the equipment can be obtained from the RJ45 socket the corresponding power).
IEEE 802.3af: This standard specifies that power supply equipment can be powered by Ethernet to power devices with power below 13W. This is enough for traditional IP telephony and webcams to meet the demand, but with the emergence of dual-band access, video telephony, PTZ video surveillance system and other high-power applications, 13W power supply is clearly unable to meet the demand for this, IEEE In 2005 began to develop a new PoE standard 802.3at (PoE Plus) to enhance PoE can transmit power.
IEEE 802.3at: IEEE802.3at (25.5W) should be born in the demand for high-power terminals, compatible with 802.3af based on the provision of greater power supply needs to meet the new needs.
Mid-Span: Use the idle cable pair that is not used in the Ethernet cable to transmit the DC power. The 4,5 feet are connected to the positive pole. The 7-8 feet are connected to the negative pole and are used in the general switch and the network terminal equipment , The Midspan PSE is a dedicated power management device that is usually connected to 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.
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. The corresponding Endpoint PSE (end-powered device) has POE-enabled Ethernet switches, routers, hubs, or other network switching devices. It is envisioned that End-Span will be quickly promoted, due to the fact that Ethernet data and transmission use common line pairs, thus eliminating the need for independent transmission of dedicated lines, which only 8-core cable and supporting the standard RJ- 45 socket is particularly important.
POE (Power Over Ethernet) refers to the existing Ethernet Cat.5 cabling infrastructure without any changes in the case, for some IP-based terminals (such as IP telephones, wireless LAN access point AP, network camera 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 wiring while ensuring the normal operation of existing networks, to minimize costs.
A complete POE system includes two parts: power supply equipment (PSE) and power supply equipment (PD). 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 a PSE load that receives power, such as POE system client devices such as IP phones, network security cameras, APs and handheld computers (PDAs) or mobile phone chargers, and many other Ethernet devices (in fact, any power No more than 13W of equipment can be obtained from the RJ45 socket corresponding power). Both based on the IEEE 802.3af standard to establish the connection of the receiving device PD, equipment type, power level and other aspects of information contact, and as a basis for the PSE through the Ethernet to the PD power supply.
The main power supply characteristics of the POE standard power supply system are:
1. Voltage between 44 and 57V, typically 48V.
2. Allow maximum current of 550mA, the maximum starting current of 500mA.
3. Typical operating current of 10 ~ 350mA, overload detection current of 350 ~ 500mA.
4. Under no-load conditions, the maximum current required is 5mA.
5. For the PD equipment to provide 3.84 ~ 12.95W three levels of power request, the maximum does not exceed 13W. (Note that PD rating 0 and rating 4 are not shown and should not be used.)
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