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发布日期:2024-03-13 12:18:52   浏览量 :163
发布日期:2024-03-13 12:18:52  

Telecommunication, often used in its plural form, is the transmission of information by various types of technologies over wireradiooptical, or other electromagnetic systems.[1][2] It has its origin in the desire of humans for communication over a distance greater than that feasible with the human voice, but with a similar scale of expediency; thus, slow systems (such as postal mail and pneumatic tube communication systems) are excluded from the field.

The transmission media in telecommunication have evolved through numerous stages of technology, from beacons and other visual signals (such as smoke signalssemaphore telegraphssignal flags, and optical heliographs), to electrical cable and electromagnetic radiation, including light. Such transmission paths are often divided into communication channels, which afford the advantages of multiplexing multiple concurrent communication sessions.

Other examples of pre-modern long-distance communication included audio messages, such as coded drumbeats, lung-blown horns, and loud whistles. 20th- and 21st-century technologies for long-distance communication usually involve electrical and electromagnetic technologies, such as telegraphtelephone, television and teleprinternetworks, radio, microwave transmissionoptical fibre, and communications satellites.

The early telecommunication networks were created with metallic wires as the physical medium for signal transmission. For many years, these networks were used for telegraph and voice services. A revolution in wireless communication began in the first decade of the 20th century with the pioneering developments in radio communications by Guglielmo Marconi, who won the Nobel Prize in Physics in 1909, and other notable pioneering inventors and developers in the field of electrical and electronic telecommunications. These included Charles Wheatstone and Samuel Morse (inventors of the telegraph), Antonio Meucci and Alexander Graham Bell (some of the inventors and developers of the telephone, see Invention of the telephone), Edwin Armstrong and Lee de Forest (inventors of radio), as well as Vladimir K. ZworykinJohn Logie Baird and Philo Farnsworth (some of the inventors of television).

With the proliferation of digital technologies since the 1960s, voice communication has been gradually supplemented by data. The limitations of metallic data transmission prompted the development of optics.[3][4][5] The development of media-independent Internet technologies provided access to world-wide services for individual users without limitations to location or time.

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