Portal:Telecommunication
The Telecommunication Portal
Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of transmission may be divided into communication channels for multiplexing, allowing for a single medium to transmit several concurrent communication sessions. 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, Philipp Reis, Elisha Gray 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...)
Selected article -
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 analogue telephony, this undulating current is directly passed through the telephone wires to a telephone exchange, and is routed to a recipient. 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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Baird in 1925 with his televisor equipment and dummies "James" and "Stooky Bill" (right) (from History of television) -
The British Broadcasting Corporation's landmark and iconic London headquarters, Broadcasting House, opened in 1932. At right is the 2005 eastern extension, the John Peel wing. (from History of broadcasting) -
The French Matra videophone (1970) (from History of videotelephony) -
AT&T Picturephone (Mod II) fully enclosed in its housing, control pad at bottom (courtesy: Richard Diehl) (from History of videotelephony) -
Oliver Lodge's 1894 lectures on Hertz demonstrated how to transmit and detect radio waves. (from History of radio) -
Tihanyi' Radioskop patent (1926) was recognized as Document of Universal Significance by the UNESCO (from History of television) -
Charles Logwood broadcasting at station 2XG, New York City, circa November, 1916 (from History of broadcasting) -
Early pioneers of radio science and technology in the United States including Charles Steinmetz, David Sarnoff, Irving Langmuir and Alfred Goldsmith in 1921, photographed next to the antenna feed wires of the New Brunswick Marconi Station, one of the first transatlantic radio links. Photo includes Albert Einstein as a visiting guest. (from History of radio) -
Private conversation, 1910 (from History of the telephone) -
Reis's telephone around 1861, first device called telephone (from History of the telephone) -
Actor portraying Alexander Graham Bell in a 1932 silent film. Shows Bell's second telephone transmitter (microphone), invented 1876 and first displayed at the Centennial Exposition, Philadelphia. (from History of the telephone) -
The master telephone patent granted to Bell, 174465, March 7, 1876 (from History of the telephone) -
The Nipkow disk. This schematic shows the circular paths traced by the holes, which may also be square for greater precision. The area of the disk outlined in black shows the region scanned. (from History of television) -
RCA 630-TS, the first mass-produced television set, which sold in 1946–1947 (from History of television) -
The Australian Broadcasting Corporation logo, first introduced in 1975 and based on the Lissajous curve (from History of broadcasting) -
The Kyocera VP-210 Visual Phone was the first commercial mobile videophone. The Personal Handy-phone System (PHS) phone was introduced in Japan (1999). (from History of videotelephony) -
In the 1920s, the United States government publication, "Construction and Operation of a Simple Homemade Radio Receiving Outfit", showed how almost any person handy with simple tools could a build an effective crystal radio receiver. (from History of radio) -
British Post Office engineers inspect Guglielmo Marconi's wireless telegraphy (radio) equipment in 1897. (from History of radio) -
Lee DeForest broadcasting Columbia phonograph records on pioneering New York station 2XG, in 1916 (from History of broadcasting) -
Typical low-cost webcam used with many personal computers (from History of videotelephony) -
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Philo Farnsworth in 1924 (from History of television) -
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Heinrich Rudolf Hertz (1856–1894) proved the existence of electromagnetic radiation. (from History of radio) -
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Thomas Edison invented the carbon microphone which produced a strong telephone signal. (from History of the telephone) -
DBS satellite dishes (from History of television) -
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Right side view, housing removed, one of its printed circuit boards exposed (courtesy: Richard Diehl) (from History of videotelephony) -
Receiver schematic, c.1906 (from History of the telephone) -
Antonio Meucci, 1854, developed a voice-communication apparatus that several sources credit as the first telephone. (from History of the telephone) -
Code of letters and symbols for Chappe telegraph (Rees's Cyclopaedia) (from History of telecommunication) -
Bell prototype telephone stamp(from History of the telephone)
Centennial Issue of 1976 -
Caricature of Sir John Reith, by Wooding (from History of broadcasting) -
Donald Manson working as an employee of the Marconi Company (England, 1906) (from History of radio) -
The master telephone patent, 174465, granted to Bell, March 7, 1876 (from History of telecommunication)
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Historical marker commemorating the first telephone central office in New York State (1878) (from History of the telephone) -
Early experiment demonstrating refraction of microwaves by a paraffin lens by John Ambrose Fleming in 1897 (from History of radio) -
Elisha Gray, 1876, designed a telephone using a water microphone in Highland Park, Illinois. (from History of the telephone) -
Reginald Fessenden, the "father" of radio broadcasting in the US (from History of broadcasting) -
Manfred von Ardenne in 1933 (from History of television) -
Reginald Fessenden (around 1906) (from History of radio) -
An exposed view of the Picturephone's rear circuit board (courtesy: Richard Diehl) (from History of videotelephony) -
Ad for the beginning of experimental television broadcasting in New York City by RCA in 1939 (from History of television) -
Top of cellular telephone tower (from History of the telephone) -
The Regency TR-1, which used Texas Instruments' NPN transistors, was the world's first commercially produced transistor radio in 1954. Size: 3×5×1.25 inch (7.6×12.7×3.2 cm) (from History of radio) -
"Fiction becomes fact": Imaginary "Edison" combination videophone-television, conceptualized by George du Maurier and published in Punch magazine. The drawing also depicts then-contemporary speaking tubes, used by the parents in the foreground and their daughter on the viewing display (1878). (from History of videotelephony) -
Philipp Reis, 1861, constructed the first telephone, today called the Reis telephone. (from History of the telephone) -
The Marconi Company was formed in England in 1910. The photo shows a typical early scene, from 1906, with Marconi employee Donald Manson at right. (from History of broadcasting)
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Broadcasting pioneer Frank Conrad in a 1921 portrait (from History of broadcasting) -
Family watching TV, 1958 (from History of television) -
A replica of one of Claude Chappe's semaphore towers (optical telegraph) in Nalbach, Germany (from History of telecommunication) -
First television test broadcast transmitted by the NHK Broadcasting Technology Research Institute in May 1939 (from History of television) -
The first mass-produced Czechoslovak TV-set Tesla 4001A (1953–57) (from History of television) -
Naomi ("Joan") Melwit and Norman Banks at the 3KZ microphone, in the late 1930s (from History of broadcasting) -
Color bars used in a test pattern, sometimes used when no program material is available (from History of television) -
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"Doc" Herrold is shown at the microphone of KQW, early 1920s. (from History of broadcasting) -
A 19th century acoustic tin can or "lovers' telephone" (from History of the telephone) -
The 1969 AT&T Mod II Picturephone, the result of decades long R&D at a cost of over $500M. (from History of telecommunication)
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Guglielmo Marconi (from History of broadcasting) -
A French Gower telephone of 1912 at the Musée des Arts et Métiers in Paris (from History of the telephone) -
The Philco Predicta, 1958. In the collection of The Children's Museum of Indianapolis (from History of television) -
The first commercial AM Audion vacuum tube radio transmitter, built in 1914 by Lee De Forest who invented the Audion (triode) in 1906 (from History of radio) -
Around 1920, radio broadcasting started to get popular. The Brox Sisters, a popular singing group, gathered around the radio at the time. (from History of radio) -
Alexander Graham Bell was awarded the first U.S. patent for the invention of the telephone in 1876. (from History of the telephone) -
1896 telephone (Sweden) (from History of the telephone) -
1917 wall telephone, open to show magneto and local battery (from History of the telephone) -
Apple iPhone smartphone (from History of the telephone) -
Reconstruction of Aeneas Tacticus' hydraulic telegraph (4th c. B.C.) in Kotsanas Museum of Ancient Greek Technology, Athens, Greece. (from History of telecommunication) -
Australian radio sets usually had the positions of radio stations marked on their dials. The illustration is a dial from a transistorised, mains-operated Calstan radio, circa 1960s. (Click image for a high resolution view, with readable callsigns.) (from History of broadcasting) -
AT&T magazine advertisement announcing commercial launch of Picturephone service. (from History of videotelephony) -
Emil Voigt, founder of 2KY on behalf of the Labor Council of New South Wales. This photo was taken in earlier days when Voight was a prominent British athlete, and winner of the Gold Medal for the five mile race at the 1908 Summer Olympics in London. (from History of broadcasting) -
The earliest photograph of a television picture, showing the face of Oliver Hutchinson in June 1926. The television picture was projected using Baird's television camera. (from History of television) -
The "Kerbango Internet Radio" was the first stand-alone product that let users listen to Internet radio without a computer. (from History of broadcasting) -
An early Smart TV from 2012 running the discontinued Orsay platform (from History of television) -
Artist's conception: 21st-century videotelephony imagined in the early 20th century (1910) (from History of videotelephony) -
Replica of the telettrofono at Museo Nazionale Scienza e Tecnologia Leonardo da Vinci of Milan, Italy, invented by Antonio Meucci and credited by several sources as the first telephone. (from History of the telephone) -
Swedish Prime Minister Tage Erlander using an Ericsson videophone to speak with Lennart Hyland, a popular TV show host (1969) (from History of videotelephony)
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Selected biography -
Guglielmo Giovanni Maria Marconi, 1st Marquess of Marconi (/mɑːrˈkoʊni/; Italian: [ɡuʎˈʎɛlmo dʒoˈvanni maˈriːa marˈkoːni]; 25 April 1874 – 20 July 1937) was an Italian electrical engineer, inventor, and politician known for his creation of a practical radio wave-based wireless telegraph system. This led to Marconi being credited as the inventor of radio and sharing the 1909 Nobel Prize in Physics with Karl Ferdinand Braun "in recognition of their contributions to the development of wireless telegraphy". His work laid the foundation for the development of radio, television, and all modern wireless communication systems.
Marconi was also an entrepreneur and businessman who founded the Wireless Telegraph & Signal Company (which became the Marconi Company) in the United Kingdom in 1897. In 1929, Marconi was ennobled as a marquess (marchese) by Victor Emmanuel III. In 1931, he set up Vatican Radio for Pope Pius XI. (Full article...)
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