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History of Television § Broadcasting

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                                                Mechanical



By the 1920s, when amplification made television practical, Scottish inventor John Logie Baird employed the Nipkow disk in his prototype video systems. On 25 March 1925, Baird gave the first public demonstration of televised silhouette images in motion, at Selfridge’s Department Store in London.Since human faces had inadequate contrast to show up on his primitive system, he televised a ventriloquist's dummy named "Stooky Bill", whose painted face had higher contrast, talking and moving. By 26 January 1926, he demonstrated the transmission of the image of a face in motion by radio. This is widely regarded as the first television demonstration. The subject was Baird's business partner Oliver Hutchinson. Baird's system used the Nipkow disk for both scanning the image and displaying it. A bright light shining through a spinning Nipkow disk set with lenses projected a bright spot of light which swept across the…

History of Television § Broadcasting

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                                                  Mechanical


Facsimile transmission systems for still photographs pioneered methods of mechanical scanning of images in the early 19th century. Alexander Bain introduced the facsimile machine between 1843 and 1846. Frederick Bakewell demonstrated a working laboratory version in 1851.Willough by Smith discovered the photoconductivity of the element selenium in 1873. As a 23-year-old German university student, Paul Jukius Gottlieb Nipkow proposed and patented the Nipkow disk in 1884. This was a spinning disk with a spiral pattern of holes in it, so each hole scanned a line of the image. Although he never built a working model of the system, variations of Nipkow's spinning-disk "image rasterizer " became exceedingly common. Constantin Perskyi had coined the word television in a paper read to the International Electricity Congress at the International World Fair in Paris on 24 August 1900. Perskyi's paper reviewed the existi…

History of Television § Broadcasting

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                                                                               History
The invention of the television was the work of many individuals in the late 19th century and early 20th century. Individuals and corporations competed in various parts of the world to deliver a device that superseded previous technology. Many were compelled to capitalize on the invention and make profit, while some wanted to change the world through visual and audio communication technology.[1] The first mechanical raster scanning techniques were developed in the 19th century for facsimile, the transmission of still images by wire. Alexander Bain introduced the facsimile machine in 1843 to 1846. Frederick Bakewell demonstrated a working laboratory version in 1851. The first practical facsimile system, working on telegraph lines, was developed and put into service by Giovanni Caserlli from 1856 onward. Willoughby Smith discovered the photoconductivity of the element selenium in 1873, laying the groundw…

History of Television § Broadcasting

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Digital television
Digital television (DTV) is the transmission of television signals, including the sound channel, using digital encoding, in contrast to the earlier television technology, analog television, in which the video and audio are carried by analog singnals. It is an innovative advance that represents the first significant evolution in television technology since color television in the 1950s. Digital TV transmits in a new image format called high definition television (HDTV), with greater resolution than analog TV, in a widescreen aspect ratio similar to recent movies in contrast to the narrower screen of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit multiple channels, up to 7, in the same bandwidth occupied by a single channel of analog television, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2006. Different digital televisio…

History of Television § Broadcasting,

Etymology
The word television comes from Ancient Greek τῆλε (tèle), meaning 'far', and Latin visio, meaning 'sight'. The first documented usage of the term dates back to 1900, when the Russian scientist Constantin Perskyi used it in a paper that he presented in French at the 1st International Congress of Electricity, which ran from 18 to 25 August 1900 during the International World Fair in Paris. The Anglicised version of the term is first attested in 1907, when it was still "...a theoretical system to transmit moving images over telegrapgh  or telephone wires". It was "...formed in English or borrowed from French télévision. In the 19th century and early 20th century, other "...proposals for the name of a then-hypothetical technology for sending pictures over distance were telephote (1880) and televista (1904). The abbreviation "TV" is from 1948. The use of the term to mean "a television set" dates from 1941. The use of the term…

History of Television § Broadcasting

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Television
Television (TV), sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrome(black and white), or in color, and in two or three dimensions and sound. The term can refer to a television set, a television program ("TV show"), or the medium of television transmission. Television is a mass medium for advertising, entertainment and news. Television became available in crude experimental forms in the late 1920s, but it would still be several years before the new technology would be marketed to consumers. After World War II, an improved form of black-and-white TV broadcasting became popular in the United States and Britain, and television sets became commonplace in homes, businesses, and institutions. During the 1950s, television was the primary medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in the US and most other developed countries. The availability of multiple types …

History of radio § Broadcasting

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                                           Radio and television
Starting in 1894, Italian inventor Guglielmo Marconi began developing a wireless communication using the then newly discovered phenomenon of radio waves, showing by 1901 that they could be transmitted across the Atlantic Ocean. This was the start of wireless telegraphy by radio. Voice and music were demonstrated in 1900 and 1906, but had little early success.World War accelerated the development of radio for military communication. After the war, commercial radio AM broadcasting  began in the 1920s and became an important mass medium for entertainment and news. World War II again accelerated development of radio for the wartime purposes of aircraft and land communication, radio navigation and radar. Development of stereo FM broadcasting of radio took place from the 1930s on-wards in the United States and displaced AM as the dominant commercial standard by the 1960s, and by the 1970s in the United Kingdom. On 25 March 1925, …

History of radio § Broadcasting

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Telecommunication

Telecommunication is the transmission of signs, signals, messages, words, writings, images and sounds or information of any nature by wire, radio, optical orother electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology. It is transmitted through a transmission media, such as over physical media, for example, over electrical cable, or via electromagnetic through space such as radio or light. Such transmission paths are often divided into communication channels which afford the advantages of multiplexing. Since the Latin term communication is considered the social process of information exchange, the term telecommunications is often used in its plural form because it involves many different technologies. Early means of communicating over a distance included visual signals, such as beacon, smoke signals, semaphore telegraphs, signal flags and optical heliographs. Other examples of…

History of radio § Broadcasting

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                                                      Etymology
The word "radio" is derived from the Latin word "radius", meaning "spoke of a wheel, beam of light, ray". It was first applied to communications in 1881 when, at the suggestion of French scientist Ernest Mercadier, Alexander Graham Bell adopted "radiophone" (meaning "radiated sound") as an alternate name for his photo phone optical transmission system.However, this invention would not be widely adopted. Following Heinrich Hertz’s discovery of the existence of radio waves in 1886, a variety of terms were initially used for this radiation, including "Hertzian waves", "electric waves", and "ether waves". The first practical radio communications systems, developed by Guglielmo Marconi in 1894-5, transmitted telegraph signals by radio waves, so radio communication was first called “wireless telegraphy”. Up until about 1910 the term "wireless tel…

History of radio § Broadcasting

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                                         Scientific research



Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1932, when Karl Jansky at Bell Telephone Laboratories observed radiation coming from the Milky Way. Subsequent observations have identified a number of different sources of radio emission. These include stars and galaxies, as well as entirely new classes of objects, such as radio galaxies, quasars, pulsars and masers.The discovery of the cosmic microwave background radiation, regarded as evidence for the Big Bang theory, was made through radio astronomy. Radio astronomy is conducted using large radio antennas referred to as radio telescope, that are either used singularly, or with multiple linked telescopes utilizing the techniques of radio interferometry and aperture synthesis. The use of interferometry allows radio astronomy to achieve high angular resolution, a…

History of radio § Broadcasting

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Remote control


Radio remote control is the use of electronic control signals sent by radio waves from a transmitter to control the actions of a device at a remote location. Remote control systems may also include telemetry channels in the other direction, used to transmit real-time information of the state of the device back to the control station. Unmanned spacecraft are an example of remote controlled machines, controlled by commands transmitted by satellite ground stations. Most handheld remote controls used to control consumer electronics products like televisions or DVD players actually operate by infrared light rather than radio waves, so are not examples of radio remote control. A security concern with remote control systems is spoofing, in which an unauthorized person transmits an imitation of the control signal to take control of the device. Examples of radio remote control: ·Unamanned aerial vechicle (UAV, drone) – A drone is an aircraft without an onboard pilot, flown by remo…

History of radio § Broadcasting

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Radio location
Radio locating is the process of finding the location of something through the use of radio waves. It generally refers to passive uses, particularly radar—as well as detecting buried cables, water mains and other public utilities. It is similar to radio navigation, but radiolocation usually refers to passively finding a distant object rather than actively one's own position. Both are types of radio determination. Radiolocation is also used in real-time locating system (RTLS) for tracking valuable assets.
Basic Principal An object can be located by measuring the characteristics of received radio waves. The radio waves may be transmitted by the object to be located, or they may be backs cattered waves (as in radar or passive RFID). A stud finder uses radiolocation when it uses radio waves rather than ultrasound. One technique measures a distance by using the difference in the power of the received signal strength (RSSI) as compared to…

History of radio § Broadcasting

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                                                     Radar

Radar is a radio location method used to locate and track aircraft, spacecraft, missiles, ships, vehicles, and also to map weather patterns and terrain. A radar set consists of a transmitter and receiver. The transmitter emits a narrow beam of radio waves which is swept around the surrounding space. When the beam strikes a target object, radio waves are reflected back to the receiver. The direction of the beam reveals the object's location. Since radio waves travel at a constant speed close to the speed of light, by measuring the brief time delay between the outgoing pulse and the received "echo", the range to the target can be calculated. The targets are often displayed graphically on a map display called a radar screen. Doppler radar can measure a moving object's velocity, by measuring the change in frequency of the return radio waves due to the Doppler effect. Radar sets mainly use high frequencies in the m…

History of radio § Broadcasting

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                                        Space communication
This is radio communication between a spacecraft and an Earth-based ground station, or another spacecraft. Communication with spacecraft involves the longest transmission distances of any radio links, up to billions of kilometers for interplanetary spacecraft. In order to receive the weak signals from distant spacecraft, satellite ground stations use large parabolic “dish antennas up to 25 metres (82 ft) in diameter and extremely sensitive receivers. High frequencies in the microwav band are used, since microwaves pass through the ionosphere without refraction, and at microwave frequencies the high gain antennas needed to focus the radio energy into a narrow beam pointed at the receiver are small and take up a minimum of space in a satellite. Portions of the UHF, L,C, S, K, and k band are allocated for space communication. A radio link which transmits data from the Earth's surface to a spacecraft is called an uplink, while…

History of radio § Broadcasting

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                                          Data communications

Wireless Networking: Automated radio links which transmit digital data between computer and other wireless devices using radio waves, linking the devices together transparently in a computer network. Computer networks can transmit any form of data: in addition to email and web pages, they also carry phone call audio, and video content Security is more of an issue for wireless networks than for wired networks since anyone nearby with a wireless modem can access the signal and attempt to log in. The radio signals of wireless networks are encrypted using WPA.

Wireless LAN: based on the IEEE802.11  standards, these are the most widely used computer networks, used to implement local area network  without cables, linking computers, laptops, cell phones, video game consoles, smart TV and printers in a home or office together, and to a wireless router connecting them to the internet with a wire or cable connection. Wireless routers i…