“It may not be long before the clerk who cooked coffee for me is simply not a person.†On the 10th, at the site of the 19th China International Industry Fair (hereinafter referred to as the “Workshopâ€), one of the visitors expressed so much emotion. In the booth of "ABB Robot", I saw a coffee robot with two gray "arms" skilled in operating the coffee machine, completed a series of coffee making processes from grinding beans, brewing and milking, and finally used Cocoa powder sprinkles a neat pattern on the surface of the coffee. The above visitors from the coffee robot "hands" connected to hot coffee, after sip a drink, said: "The taste and 'living coffee' is no difference." The ICT Robotics Exhibition started from a 7,000-square-meter exhibition area in 2012 and has exceeded 56,000 square meters. It has become the robot exhibition with the largest area, the most complete brand, and the longest line of exhibiting robots. The various practical robots debuted at this year's Industry Fair also showed the robot's "intimate" side, presenting the interesting possibility of "human-computer coexistence" in the future life. In the near future, it may not be the security guard who directs you to reload your car. Instead, it is a “sprouting†property robot. On the same day, the reporter saw a series of intelligent robots that will “strengthen their feet†in the property sector. Guo Rufeng, an engineer at Guoji Intelligent Technology Co., Ltd., said that relying on face recognition technology, intelligent robots can distinguish residents and visitors and decide whether to let them go. It also discourages uncivilized behavior such as smoking and fighting. After updating the relevant information through the Internet, it can even identify the wanted suspects. 300 sorting “Huang Huangren†was formally placed at the Central Bureau of Anhui Post Hefei Post District the day before, preparing for “Double 11â€. Reporters learned from the Industry Fair that in addition to sorting parcels, robots can do a lot in the field of logistics. Yu Yingying, sales manager of Hangzhou Haikang Robotics Co., Ltd., said that the intelligent storage robot system developed by the company uses a mobile robot as a carrier to extend a series of intelligent handling robots, intelligent sorting robots, and intelligent parking robots to achieve warehousing. Unmanned management. In addition to providing assistance, robots also "take risks." A "painting robot" debuted at this year's Industry Fair, which is expected to replace manual operations to reduce the health hazards of paint to construction workers. According to Dai Cheng, Key Account Manager of Shanghai KUKA Roboter Co., Ltd., this “painting robot†consists of a small six-axis robot that can be customized for each different customer project. He said that there is a risk of explosion during the painting process, so the “painting robot†robot arm is specially designed for explosion protection. As the annual exhibition of China's “industrial wind vaneâ€, the 19th year of the Industrial Fair has never missed Bo’s eyeball robot. The once amazing "black technology" is now getting closer to the real life scene. Qu Daokui, president of Shenyang Xinsong Robot Automation Co., Ltd. believes that the addition of artificial intelligence will allow the development of robotics to enter a new stage, and the “Android 2.0 era†has come. Unlike traditional concept robots, intelligent robots have become more and more closely related to human life, health, culture, education, and so on. Classic Ethernet uses a long cable meandering around the building, and this cable connects all the computers. The architecture of classic Ethernet is shown in the following figure "Ethernet": Rf Port Onu,Pon Technology,Catv Port Shenzhen GL-COM Technology CO.,LTD. , https://www.szglcom.com
Physical layer
Each version of Ethernet has a maximum cable length limit (that is, the length that does not need to be amplified). Signals within this range can be transmitted normally, and signals beyond this range will not be transmitted. In order to allow the construction of a larger network, multiple cables can be connected with repeaters. A repeater is a physical layer device that can receive, amplify, and retransmit signals in both directions.
On these cables, the transmission of information uses Manchester encoding.
MAC sublayer
Classic Ethernet uses 1-adhere to the CSMA/CD algorithm, that is, when the station has a frame to send, it must listen to the medium, and send it immediately once the medium becomes free. Monitor whether there are conflicts on the channel while they are being sent. If there is a conflict, immediately terminate the transmission, and send a short conflict enhancement signal, and then wait for a random period of time before resending.
The development of Ethernet is very fast, starting to evolve from the typical Ethernet structure of a single long cable. The problems of a single cable, such as finding out the connection-related problems such as broken or loose locations, have driven people to develop a different type of wiring mode. In this mode, each station has a dedicated wire connected to a central hub. The hub simply connects all the connecting wires electrically, like soldering them together. Hubs cannot increase capacity because they are logically equivalent to classic Ethernet with a single cable. As more and more stations join, the share of fixed capacity shared by each station decreases. Eventually, the LAN will be saturated.
There is another way out to handle the ever-increasing load: switched Ethernet. The core of switched Ethernet is a switch, which contains a high-speed backplane that connects all ports. From the outside, switches look like hubs. They are a box, usually with 4-48 ports, and each port has a standard RJ-45 connector for connecting twisted-pair cables. The switch only outputs the frame to the port where the frame wants to go. A machine can be added or deleted by simply plugging in or unplugging the cable, and since the flaky cable or port usually only affects one machine, most errors are easy to find. This configuration mode still has the problem of a shared component failure, that is, the failure of the switch itself: if all stations lose network connectivity, the IT staff knows how to solve this problem: replace the entire switch.