Portal:Telecommunication
The Telecommunication Portal
Telecommunication, often used in its plural form, is the transmission of information with an immediacy comparable to face-to-face communication. As such, slow communications technologies like postal mail and pneumatic tubes are excluded from the definition. Many transmission media have been used for telecommunications throughout history, from smoke signals, beacons, semaphore telegraphs, signal flags, and optical heliographs to wires and empty space made to carry electromagnetic signals. These paths of transmission may be divided into communication channels for multiplexing, allowing for a single medium to transmit several concurrent communication sessions. Several methods of long-distance communication before the modern era used sounds like coded drumbeats, the blowing of horns, and whistles. Long-distance technologies invented during the 20th and 21st centuries generally use electric power, and include the telegraph, telephone, television, and radio.
Early telecommunication networks used metal wires as the medium for transmitting signals. These networks were used for telegraphy and telephony for many decades. In the first decade of the 20th century, a revolution in wireless communication began with breakthroughs including those made in radio communications by Guglielmo Marconi, who won the 1909 Nobel Prize in Physics. Other early pioneers in electrical and electronic telecommunications include co-inventors of the telegraph Charles Wheatstone and Samuel Morse, numerous inventors and developers of the telephone including Antonio Meucci and Alexander Graham Bell, inventors of radio Edwin Armstrong and Lee de Forest, as well as inventors of television like Vladimir K. Zworykin, John Logie Baird and Philo Farnsworth.
Since the 1960s, the proliferation of digital technologies has meant that voice communications have gradually been supplemented by data. The physical limitations of metallic media prompted the development of optical fibre. The Internet, a technology independent of any given medium, has provided global access to services for individual users and further reduced location and time limitations on communications. (Full article...)
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The carbon microphone, also known as carbon button microphone, button microphone, or carbon transmitter, is a type of microphone, a transducer that converts sound to an electrical audio signal. It consists of two metal plates separated by granules of carbon. One plate is very thin and faces toward the speaking person, acting as a diaphragm. Sound waves striking the diaphragm cause it to vibrate, exerting a varying pressure on the granules, which in turn changes the electrical resistance between the plates. Higher pressure lowers the resistance as the granules are pushed closer together. A steady direct current is passed between the plates through the granules. The varying resistance results in a modulation of the current, creating a varying electric current that reproduces the varying pressure of the sound wave. In telephony, this undulating current is directly passed through the telephone wires to the central office. In public address systems it is amplified by an audio amplifier. The frequency response of most carbon microphones, however, is limited to a narrow range, and the device produces significant electrical noise.
Before the proliferation of vacuum tube amplifiers in the 1920s, carbon microphones were the only practical means of obtaining high-level audio signals. They were widely used in telephone systems until the 1980s, while other applications used different microphone designs much earlier. Their low cost, inherently high output and frequency response characteristic were well suited for telephony. For plain old telephone service (POTS), carbon-microphone based telephones can still be used without modification. Carbon microphones, usually modified telephone transmitters, were widely used in early AM radio broadcasting systems, but their limited frequency response, as well as a fairly high noise level, led to their abandonment in those applications by the late 1920s. They continued to be widely used for low-end public address, and military and amateur radio applications for some decades afterward. (Full article...)General images
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Paul Julius Gottlieb Nipkow (22 August 1860 – 24 August 1940) was a German technician and inventor. He invented the Nipkow disk, which laid the foundation of television, since his disk was a fundamental component in the first televisions. Hundreds of stations experimented with television broadcasting using his disk in the 1920s and 1930s, until it was superseded by all-electronic systems in the 1940s.
Nipkow has been called the "father of television", together with other early figures of television history like Karl Ferdinand Braun. (Full article...)Did you know (auto-generated) -
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