Human beings have a long history of communication. As early as ancient times, people exchanged information through simple language and murals. For thousands of years, people have been using language, symbols, bells and drums, fireworks, bamboo slips and paper books to convey information. Ancient bonfires, flying pigeons and post-horse mail are examples of this. Some primitive tribes in some countries still retain ancient communication methods such as beating drums and blowing horns. In modern society, the command sign language of traffic police and the semaphore in navigation are just the result of the further development of ancient communication methods. These basic aspects of information transmission depend on human vision and hearing.

/kloc-After the middle of the 9th century, with the development of telegraph and telephone and the discovery of electromagnetic waves, fundamental changes have taken place in the field of human communication, realizing the transmission of information through metal wires and even wireless communication through electromagnetic waves, making the mythical "clairvoyance" and "clairvoyance" come true. Since then, human information transmission can be separated from the conventional audio-visual way, using electrical signals as a new carrier, bringing a series of iron technological innovations and opening a new era of human communication.

From 65438 to 0837, American Samuel Morse successfully developed the world's first electromagnetic telegraph. Using his own code, he can convert information into a series of long or short electrical pulses to the destination, and then convert them into original information. 1844 On May 24th, Morris sent the first telegram in human history in the conference hall of the Federal Supreme Court of the Capitol, thus realizing long-distance telegraph communication.

1864, the British physicist J.c.Maxwel established a set of electromagnetic theories, predicted the existence of electromagnetic waves, and explained that electromagnetic waves and light have the same properties and both travel at the speed of light.

1875, the Scottish youth A.G. Bell invented the world's first telephone. And applied for an invention patent in 1876. 1878, the first long-distance telephone experiment was conducted between Boston and new york, which are 300 kilometers apart, and it was successful. Later, the famous Bell Telephone Company was established.

1888, the young German physicist H.R. Hertz conducted a series of experiments with radio circuits and discovered the existence of electromagnetic waves. He proved Maxwell's electromagnetic theory by experiments. This experiment caused a sensation in the whole scientific community and became an important milestone in the history of modern science and technology, which led to the birth of radio and the development of electronic technology.

The discovery of electromagnetic waves had a great influence. In less than six years, Russian popov and Italian Marconi invented wireless telegraph respectively, which realized the radio transmission of information, and other radio technologies mushroomed. 1904 British electrical engineer Fleming invented the diode. 1906 American physicist Fessenden successfully developed radio broadcasting. 1907, American physicist Trevor Lester invented the vacuum triode, and American electrical engineer Armstrong invented the superheterodyne receiving device by using electronic devices. American radio expert Conrad established the world's first commercial radio station in Pittsburgh on 1920. Since then, the broadcasting industry has flourished all over the world, and broadcasting has become a convenient way for people to understand current events. 1924, the first short-wave communication line was established between nauen and Buenos Aires. 1933, the first commercial microwave radio line between Britain and France was established in Clarville, France, which promoted the further development of radio technology.

The discovery of electromagnetic waves has also promoted the rapid development of image communication technology. 1922, 16-year-old American middle school student Philo Farnsworth designed the first schematic diagram of TV fax. 1929 applied for an invention patent and was ruled as the first person to invent television. From 65438 to 0928, Zwojin of Westinghouse Electric Company invented the photoelectric picture tube, and cooperated with the engineering teacher Gas to realize the transmission and transmission of electronic scanning TV. 1935, the Empire State Building in New York, USA, set up a TV station. The next year, TV programs were successfully transmitted to places 70 kilometers away. 1938, Volgin made the first TV camera that meets the practical requirements. After people's continuous exploration and improvement, 1945, American radio company made the world's first all-electron-tube color TV according to the working principle of three primary colors. Until 1946, American Ross Weimar invented the high-sensitivity camera tube. In the same year, Professor Hamoto, a Japanese, solved the receiving antenna problem of home TV. Since then, some countries have successively established ultrashort wave relay stations, and television has rapidly spread.

Image fax is also an important communication mode. Since 1925, the first practical fax machine was developed by American radio company, and the fax technology has been continuously innovated. Before 1972, this technology was mainly used in news, publishing, meteorology and broadcasting industries; From 1972 to 1980, fax technology has completed the transformation from analog to digital, from mechanical scanning to electronic scanning, and from low speed to high speed. In addition to transmitting meteorological maps, press releases, photos and satellite cloud pictures instead of telegrams, it has also been applied in medical treatment, library management, information consultation, financial data, electronic post and so on. After 1980, fax technology was transformed into an integrated processing terminal, which not only undertakes communication tasks, but also has the ability of image processing and data processing, and became an integrated processing terminal. Electrostatic copiers, tape recorders, radars and lasers are all important inventions in the history of information technology.

In addition, remote control, telemetry and remote sensing technology are also very important technologies as information remote control. Remote control is a technology that uses communication lines to control remote controlled objects, which is applied in electrical industry, oil pipeline, chemical industry, military and aerospace industry. Telemetry is a measurement technology, which converts the measured physical quantities to a distant place, such as voltage, current, air pressure, temperature, flow and so on. , converted into electricity, transmitted to observation points through communication lines, and applied to meteorological, military, aerospace and other industries. Remote sensing is a comprehensive measurement technology, which uses sensors to receive electromagnetic wave information radiated by high-altitude or distant objects, and prompts the nature, shape and changing trend of the measured objects through processed or recognizable images or recording tapes used by computers. It is mainly used in meteorology, military affairs, aerospace and other fields.

With the rapid development of electronic technology, the computing tools urgently needed by military and scientific research have also been greatly improved. 1946, eckert and Moses of the University of Pennsylvania developed the world's first electronic computer. The innovation of electronic components and materials further promotes the development of electronic computers in the direction of miniaturization, high precision and high reliability. In the 1940s, scientists discovered semiconductor materials and used them to make transistors instead of electron tubes. 1948, shockley, Badin and Bratin of Bell Laboratories invented transistors, so transistor radios, transistor televisions and transistor computers quickly replaced various vacuum tube products. 1959, kilby and Noyce of the United States invented integrated circuits, and microelectronics technology was born. LSI was born in 1967. More than 1000 transistor circuits can be integrated on a silicon wafer the size of a grain of rice. 1977, American and Japanese scientists made VLSI and integrated130,000 transistors on a 30-square-millimeter silicon wafer. Microelectronics technology has greatly promoted the upgrading of electronic computers, making them show unprecedented information processing functions and become an important symbol of modern high technology.

In order to solve the problem of resource sharing, stand-alone computers have rapidly developed into computer networking, realizing data communication and data sharing between computers. Communication media has developed from ordinary wires and coaxial cables to twisted pair, optical fiber lines and optical cables; The input and output devices of electronic computers have also developed rapidly. Scanner, plotter, audio and video equipment, etc. Make the computer more powerful and can handle more complex problems. With the rise of multimedia technology in the late 1980s, computers have the ability to comprehensively process various forms of information, such as words, sounds, images, movies, etc., and are increasingly becoming the most important and essential tool for information processing.

At this point, we can preliminarily think that information technology (IT) is a comprehensive technology based on microelectronics and photoelectric technology, supported by computer and communication technology, and with information processing technology as the theme. The close combination of electronic computer and communication technology marks the arrival of the digital information age.

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History of communication development

line telecommunications

American Morse (F.B.Morse): The telegram is about 5 kilometers (dots, dashes, spaces → letters and numbers);

American Bell (A.G.Bell): patented telephone (electric signal → voice);

Pubin, USA: communication cable;

1972 Japan: data communication and fax communication services of public communication network;

USA: Publishing Bell Data Network, UK: Image Information Service Experiment;

Modern communication systems use some centralized exchange facilities → complex information networks.

→ "exchange function" → realize signal transmission between any two points.

wireless communication

Maxwell, England, 1864: hypothesis of electromagnetic wave;

1888 H Hz: confirm the existence of electromagnetic wave;

1895 Marconi, Italy: wireless communication, the transmission distance is only a few hundred meters;

Italy Marconi 190 1: Wireless communication across the Atlantic;

1938 French ribbon: PCM mode;

1940 CBS: color TV experiment broadcast;

195 1 American CBS: official broadcast of color TV;

Modern wireless communication is spread all over the world and leads to the universe.

Such as GPS, its accuracy can reach tens of meters.

The development history of mathematical analysis methods

First, Fourier analysis

1822 French mathematician J. Fourier: laid the theoretical foundation of Fourier series;

Poisson, Gaussian: applied to electricity;

19 capacitors used in engineering practice → processing sinusoidal signals of various frequencies;

In the 20th century, resonant circuits, filters and sinusoidal oscillators expanded their application fields.

Second, Laplace transform.

O. 19 British engineer Heaviside: operation method (operator method)-pioneer;

French mathematician P.S. Laplace: Laplace transformation method;

After 1970s, CAD solved the problem of circuit analysis → replacing Laplace transform.

The development of other systems, such as discrete →

Third, Z-transform.

1730 British mathematician de Morville: generating function-similarity;

Laplace's Contribution in19th Century

H. the seal of the twentieth century: contribution;

Application of sampling data control system →Z transform in 1950s and 1960s.

Research and Practice of Digital Computer

Fourth, the state equation analysis

Classical linear system theory (external characteristics) in 1950s;

Modern linear system theory (internal characteristics) In the 1960s,

R. Kalman: state space method.