In 1930s, 65438+2009, after the successful test of cable and telegraph communication, the telecommunication industry using electromagnetic system to transmit information developed rapidly. Its rise and development has roughly experienced four periods: the invention and application of telegraph, the invention and application of telephone, the development and application of large-capacity automatic communication network and the birth and development of digital communication.
The invention and application of telegraph is the beginning of electronic communication. People can send text messages quickly over long distances by telegraph. 1835, American S.F.B Morse created Morse code for telegraph communication. 1837, with the help of mechanic a.l. Weil, he developed an electromagnetic telegraph (later called Morse manual telegraph), which was successfully tested in new york. Since then, Morse manual telegraph and Morse code have been widely used all over the world. Telegrams were originally transmitted by overhead iron lines and could only be used on land. 1850, Britain laid submarine cables in the English Channel. 1866, submarine cables across the Atlantic Ocean were successfully laid, realizing transoceanic telegraph communication. Later, many submarine cables were laid between continents and coastal areas, forming a global telegraph communication network.
The development of telegraph technology has been nearly 150 years. Telegraph equipment has developed from Morse manual telegraph operated by human beings to electronic teletypewriter with a high degree of automation, and telegraph transmission has also developed from wired transmission to radio transmission, from direct current telegraph signal transmission to multi-channel audio carrier telegraph transmission. With the emergence of new technologies such as computer, data communication, satellite communication and optical fiber communication, telegraph communication is further developing towards electronization and automation. In addition, there have been faxes and telegrams that directly transmit information such as words, charts and photos.
The invention and application of the telephone A.G. Bell, an American scientist born in Scotland, invented the telephone in 1876. With the telephone, people can talk over a long distance. The earliest commercial telephone office was established in New Haven, USA in 1878, with 2 1 users. 1880, many cities have also set up telephone lines and opened long-distance calls. Some European countries have also set up telephone offices. The early telephone calls were very simple, with unclear voice and not far away. The invention of carbon powder microphone changed the single iron wire of voice transmission into double copper wire, which improved the call quality and increased the call distance. 1899, Professor M.I. Puping of the United States successfully adopted induction technology, which increased the communication distance of telephone transmission by cable by more than three times. 1906 L.D. forest invented the triode electron tube; Later, long-distance telephone communication was realized by using a repeater made of electron tubes. After the application of electronic tube in radio communication, it greatly surpassed the original spark transmitter and promoted the development of radio communication and radio broadcasting. It is more economical and convenient to use short-wave radio in overseas communication than submarine telegraph cable, which can communicate not only by telegraph but also by telephone. During this period, telephone switching technology has also developed greatly. At first, a magnetic telephone exchange was used, with only a few hundred telephone users at most. With the increase of users, a telephone exchange has appeared, which can have thousands of users. 1889a.b. Strowger invented the automatic exchange step telephone exchange, which can accommodate more users' telephones, which is not only convenient to use, but also saves a lot of operators. Subsequently, automatic telephone equipment such as crossbar telephone exchange system and semi-electronic telephone exchange came out one after another, which promoted the greater development of telephone communication.
Development and application of large-capacity automatic communication network19In the 1990s, telephone communication has been quite developed. Automatic telephone exchanges have been installed in major cities around the world, and the number of telephone users has increased. The demand for long-distance calls has increased rapidly, which requires large-capacity long-distance transmission equipment, overhead lines and long-distance cables to increase the capacity of transmitting calls. In this case, the carrier phone appears in 19 18, and four phones can be opened on a pair of copper wires. 194 1 year, 480 telephones can be opened on coaxial cable, and later it developed to 1800, 2700 or even 10000 multi-channel telephones. In the early 1950s, microwave relay was used in radio communication. Because of its fast construction speed and low cost, it can save a lot of copper and lead, and it can cross areas where cables cannot be laid, so it was quickly adopted by various countries. 1800 ~ 2700 carrier phone can also be installed on microwave lines, and the communication ability is greatly improved. The development of coaxial cable and microwave relay communication has laid the foundation for the construction of national automatic long-distance telephone network. Many countries, such as the United States, Japan and Britain, built national long-distance telephone automation networks in the 1950s and 1970s. Due to the development of satellite communication and the construction of submarine coaxial telephone cable, the automation of international telephone was widely popularized in the 1960s and 1970s.
Birth and development of digital communication 1939, British A.H. Reeves invented pulse code modulation, which can convert analog signals used in telephone communication into digital signals for a long time, but at that time, electronic tubes were used, which were too expensive and difficult to popularize. After the invention of 1948 transistor, 1962 made 24-channel pulse code modulation equipment, which was applied to local communication network. The appearance of integrated circuits, especially large-scale integrated circuits, in the 1960s made pulse code modulation easy. 1975 pulse code modulation equipment has been multiplexed to 4032 channels. At the same time, the program-controlled electronic exchange has also been successfully developed, which has the conditions for the development from analog network to digital network. The use of digital communication has greater advantages for telegraph and data communication, and the transmission efficiency of digital telephone circuit can be improved by ten to dozens times than that of analog telephone circuit. In the era of vigorously promoting the application of electronic computers in various fields, data communication occupies an important position. In addition, modern transmission equipment such as optical fiber communication transmits digital signals. If digital signals are used, satellite communication can also improve efficiency. Therefore, the communication network is developing from analog network to digital network. Various telecommunications services, including telephone, telegraph, data, fax, images, etc. Will be merged into a communication network. This kind of communication network is called integrated services digital network.
Overview of China Telecom Development 187 1 year, Danish Dabei Telegraph Company privately laid a water line (submarine cable) in China, and set up a telegraph office in the Shanghai Concession to start telegraph business. 188 1 year, Shanghai yingshang ruiji foreign firm established huayang telephone company to install telephones in the British concession. 1897 During the German occupation of JIAOZHOU Bay in Shandong, China, a post office was set up in Qingdao to handle postal, telegraph and local telephone services. 1900, Danish C.O.P Poulsen took advantage of Eight-Nation Alliance's invasion of China to install a telephone in Tianjin, reaching Tanggu and Beitang directly, and extended the telephone line to Beijing on 190 1. Since 1905, the China municipal government has successively taken back the telephones in Beijing, Tianjin and Jingu, the seashore lines from Songhu, Shanghai to Yantai, Dagu and Yantai to Ahava (now Weihai), the radio stations in Shanghai, Qingdao, Jinan and Harbin, and the telegraph receiving and dispatching offices set up in Shanghai by three telegraph companies: Dadong, Dabei and Pacific. When foreign countries invaded China's telecommunication rights, China also operated its own telegraph, telephone and radio communication services.
Self-made telegraph: 1877, the Qing government built a military telegraph line from Tainan to Qihou (now Kaohsiung) in Taiwan Province Province. 1879, a military telegraph line was set up between Tianjin and Dagukou and Beitang Haikou Fort. 188 1 year, the Tianjin-Shanghai telegraph line along the Beijing-Hangzhou Grand Canal was completed, with a total length of 3,075 miles. The telegraph headquarters is located in Tianjin, and there are seven telegraph branches along the way. Starting from 188 1 This is the beginning of public telecommunication service in China. 1882, the Qing government recruited commercial shares, recovered government investment, and changed the telecom construction and operation into official supervision and commercial office. By 1902, telegraph lines from Tianjin to Beijing, Shanghai to Guangzhou, Nanjing to Wuhan, and Wuhan to Chongqing were built one after another. At the same time, provincial telegraph lines have been built in more than 20 provinces and autonomous regions, connecting most cities above the state capital, and public telegraph services have been opened in these cities. By 1935, more than 73,000 kilometers of telegraph lines have been built in China. Morse manual telegraph has been installed since China started telegraph business. 190 1 year later, use Weston automatic transceiver. In the early 1940s, teletypewriters, carrier telegrams and photo fax machines were installed in a few cities.
Self-operated telephone: 1899, the Qing government stipulated that telegraph offices also run telephone services, and local telephones were installed in major cities and some medium-sized cities in China, all of which adopted magnet telephone exchanges. Since 1925, it has been converted into an automatic telephone exchange in some cities. 1935, 85,000 local telephones were installed in China, including official telephones and business telephones. From 1905 to 1934, more than 27,000 kilometers of short-distance long-distance telephone lines have been built. 1935, more than 3,000 kilometers of copper wires were built between Hebei, Henan, Hubei, Hunan, Shandong, Jiangsu, Zhejiang, Jiangxi and Fujian provinces, voice amplifiers and one-way carrier phones were installed, and long-distance calls were opened. After 1937, it was expanded to other provinces, using three-way carrier phones.
Self-run radio communication: China's radio station construction started with military communication. 1899 The Governor of Guangdong and Guangxi set up radio stations in Guangzhou Governor's Office, Makou, Qianshan and other fortresses and larger warships. On 1905, beiyang fleet installed radio stations on Nanyuan, Baoding, Tianjin Hangying and four warships. 1907 In order to solve the direct communication between Chongsong and Chongsong, radio stations were installed in Wusong and Chongming in Jiangsu Province. Since 19 12, radio stations have been established in Beijing, Zhangjiakou, Wuchang, Fuzhou, Guangzhou, Lanzhou, Dihua (Urumqi) and Fengtian (Shenyang). After the Northern Expeditionary Army 1927 arrived in Shanghai, it set up a factory to manufacture short-wave radio transceivers, and successively set up short-wave radio stations in major cities across the country. Starting from 1929, international transceiver stations will be built in Shanghai Fenglinqiao, Zhenru, Liuhang and other places, and high-power transmitters will be installed. Since 1930, the station has successively established radio direct dial telegraph circuits with San Francisco, Berlin, Paris, Geneva, Saigon, London, Moscow and Tokyo. At this time, China's international telegraph communication has begun to take shape.
At the same time, 1928, the Central Committee of the Communist Party of China established a secret radio station in Shanghai. In order to facilitate the Central Committee's contact with Party organizations such as the Southern Bureau, the Yangtze Bureau and the Northern Bureau in Shanghai, 1930 successively established radio stations in Kowloon, Tianjin, southeastern Jiangxi, Hubei, Henan and Anhui, and western Hunan and Hubei (Honghu), and in the same year established the Red Army Radio Brigade. With the successful development of China Revolution, the radio communication network has been formed and played a great role in the revolution.
Construction and Development of New China Telecom 1949 After the establishment of People's Republic of China (PRC), long-distance telecommunication lines from Beijing to major cities in China were quickly built and restored. 1952, China's main trunk lines opened 12 carrier telephone, and 60 symmetrical cable carrier systems were built in 1960s. At the beginning of 1976, coaxial cable 1800 carrier system was opened from Beijing to Shanghai and Hangzhou. In 1975, 600 and 960 microwave relay communication lines were built, with a length of 14000 kilometers, reaching 19 provincial capitals and autonomous region capitals, and undertaking the transmission tasks of telephone, telegraph communication, newspaper fax and TV broadcast programs. At the end of 1970s, the optical fiber communication system was developed and tried out on the trunk lines between local telephone offices. With the development of telecom construction, the demand for communication in society is increasing day by day, and various telecom services and communication capabilities are also increasing accordingly. 1949 and 1983, the business volume and equipment of China Telecom are shown in the table.
With the development of local telephone and long-distance communication network, 1976 opened automatic long-distance telephone dialing service between eight cities including Beijing, Tianjin and Shanghai. By the end of 1983, automatic or semi-automatic long-distance telephone dialing service was opened between 26 provincial capitals and 50 special cities. The proportion of local telephone automatic exchange is gradually expanding. At the end of 1983, automatic telephone exchanges accounted for 75 17% of the 2.622 million local telephone exchange equipment in China. Public telegraph communication has installed computer-controlled automatic transmission equipment in five cities, including Shanghai and Guangzhou. The number of telegrams exchanged by automatic relay equipment accounts for 79.9% of the total exchange volume in these five cities. In terms of international communication, short-wave radio communication has changed to satellite communication, and international satellite communication earth stations have been established in Beijing and Shanghai. By the end of 1983, telephone direct dialing and telegraph direct dialing circuits had been opened with 45 countries and regions.
The experimental communication satellite launched by China on April 8, 1984/kloc-0 was fixed over the equator on April 6/east longitude 125 degrees 18: 27: 57, and the instruments and equipment on the satellite worked well. Subsequently, the transmission experiments of telephone, radio and color TV were carried out, and the images were clear and the sound was good. It marks the new development of communication technology in China.
1956 nationwide conference telephone service can be opened step by step in Beijing, provincial capitals, regions, counties and communes (townships), or it can be opened to counties (or communes) at one time from Beijing or provincial capitals. In the 1960s, more than 20 large and medium-sized cities in China opened the photo fax service and newspaper fax service in 13 city. The telex service has developed from 503 users in 1980 to 1373 users in 1983. In terms of data communication, low-speed data communication networks have been opened among 60 cities in China since 1980. 1982 During the third national census, the medium-speed (1200 bit/s) data communication network connecting 20 electronic computers began to be used.
Since 1950s, China has established electronic industry and telecommunication industry, and successively designed and manufactured various telecommunication technical equipment. Such as teletypewriter, fax machine, long-distance and local automatic telephone exchanges, various communication cables and carrier equipment, microwave relay communication equipment, computer-controlled automatic telegraph relay equipment, satellite earth station equipment, optical fiber communication equipment and various automatic test instruments, basically meet the needs of our country and provide conditions for further development of telecommunications.