Learn PoE take a look at how the power supply cable

       Whether it is easy to buy most of the Hub is a set of five wireless AP, will be included in an attachment to the first side brain Saddam thick black AC transformer. But do not have telephone, telephone line because it is charged enough to support the phone's power needs, and even many string ext 2 Units also not be affected much. Now that the example of telephone through a communication line at the same time electricity is feasible, why not directly to the device via Ethernet to supply it? This is called "Power over Ethernet" technology (Power over Ethernet technology) In fact, as early as 6 years ago at launch, IEEE Standard No. 802.3af, referred to as PoE.

     Origin of PoE and 802.3af Power-over-Ethernet technology, the starting point is to allow IP phone, WLAN access points, network cameras can be first-class small network equipment directly from the Ethernet access to the power line, it goes without a separate power line laying; to simplify the system cabling and reduce network infrastructure costs. Four pairs of twisted pair through the two pairs of free to transmit power. At PoE systems, the provision of electricity is called "power equipment" (PSE, Power Sourcing Equipment), and the use of power is called the "electric equipment" (PD, Power Device). PSE is responsible for the power into the Ethernet cable, and the implementation of the planning and management of power. PSE has two types: "Endpoint PSE", the other is "Midspan PSE". Endpoint PSE function is to support the PoE Ethernet switch, router, hub or other network switching equipment. Midspan PSE is a dedicated power management devices, and switches are usually together. It corresponds to each port has two RJ45 jacks, a switch connected to the use of short-term, and the other to connect the remote equipment. PD may take many forms, such as IP phone, AP, PDA or mobile phone charger, etc. - in fact, any power the device no more than 13W from the RJ45 socket can obtain the corresponding power. 3Com Air Connect Wireless Access Point (PD) with Power Base T module (Midspan PSE) is an early successful application of the use of the classic examples of PoE. In this manner, the user can be hoisting the AP at墙顶, without taking any account of the vicinity are not there is a power outlet.

     In order to standardize and promote the development of PoE applications, IEEE 802.3 Working Group in 1999 began to draw up the IEEE 802.3af standard, as an extension of the Ethernet standard. June 2003 standard finally adopted by the network of power supply, transmission and reception have been good detail. Users in the design of PoE applications, must strictly comply with these provisions, the purchase of certified products, to be able to directly access to reliable power from the Ethernet.

     802.3af detail the benefits to one basket 802.3af our benefits too numerous to mention.

     First, it can effectively reduce the wall power socket connected to the quantity of equipment. Think of our desk: a host PC and displays the need for a three-hole on the socket, even if employees do not need to connect an ordinary scanner, printer and other peripherals, but usually require more power to connect the PDA base socket, IP mobile phone charger that - these devices are not universal AC power supply. Therefore common to all interpolation line between the working position to drag拉去board, not only may lead to circuit overload and tripping, and security can not be underestimated. As the only global power standard, 802.3af power demand can simultaneously support different Ethernet equipment. In addition to common wireless AP, a well-known manufacturer of instruments in 2003 at Gibson United 3Com has developed to support the PoE's first electric guitar figure, and even have a network PowerDsine original equipment manufacturers to produce a razor PoE.

    Secondly, 802.3af is greatly facilitated by the power socket in the absence of places to install equipment, or even derived a lot of new applications. 802.3af is driving the video surveillance network and Ethernet integration process. In addition to the deployment process has been simplified, based on the PoE system to be able to be placed before the camera can not because it is difficult to deploy AC power supply and the location of installation, and security access to the internal power supply. 802.3af also help to promote the popularity of RFID technology applications to support 802.3af the RFID reader can be connected with the Ethernet switch to a new real-time transmission of information to track the location of tags. At present, such products Cisco has been the United States at two major hospitals has been applied. All in all, 802.3af means that as long as they are able to place the deployment of Ethernet cables, you can install a lot of easy to install new equipment.

    802.3af enterprises can also give money. 802.af eventually take part in a protocol developed by such experts have cited a number of comparative data: a network to support Power over Ethernet terminals will increase the cost of less than 70%, with the cost of PSE switches improve function less than 25%; but because of removing conventional electrical wiring and power socket, the user can save at least 50% of the total costs. At large-scale deployment of WLAN and IP phone in a modern office environment, the application of cost-effective 802.af programs have become more prominent.

    "Digital signature" technology and the problems to be solved

     Speaking in front of "802.3af power demand can simultaneously support different Ethernet equipment," a bit incredible, right? Achieve this goal have relied on the standard equipment for each's own "Digital Signature." When the terminal equipment connected to a start-up in line with the 802.3af standard PSE switch function, the switch will find the end of the "Digital Signature." If no signature, only the equipment on the general data connection, no power transmission. If it is found that the "digital signature", switch will be carrying out a data connection at the same time in accordance with the 802.3af Signature Level information to the power transmission equipment. Based on the "digital signature", 802.3af Power Supporting point-to-multipoint connection. So as long as the switches and uninterruptible power supply connected, you can protect at least a greater power when the network communication can be business as usual. IEEE 802.3af Task Force Chairman Steve Carlson in the standard release have been predicted at the beginning of the next decade, all the Ethernet switches will support both PoE; but a few years, 802.3af application has not as expected. In addition to the development because it depends on the WLAN and the popularity of IP telephone, the existence itself of some much-needed in the application of practical problems - heat dissipation between the wiring and electrical environment, we need to re-design. At enterprise-class applications, which has a distribution of the Ethernet ports on the hundreds of possible. If the 400 as an example, each in accordance with the standard Ethernet ports 802.af power output of 15W, only on the need to increase power over Ethernet 6KW. Electricity demand will increase the direct cause of the UPS system was originally designed overwhelmed, and the increase in energy consumption, wiring between the environment and the cooling demand have changed, and may greatly increase the room with the switches, servers and other equipment due to overheating the probability of downtime.