/kloc-After the middle of the 0/9th century, with the invention of telegraph and telephone and the discovery of electromagnetic waves, the communication field of human beings has undergone fundamental changes, realizing the transmission of information by metal wires and even wireless communication by electromagnetic waves, making the mythical "clairvoyance" and "clairvoyance" become a reality. 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.