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Aug 4, 2015 · Radio and TV are two communication technologies that blossomed in the 20th century. Television transmits images and audio while radio transmits only audio. Radio and TV and print were the significant mediums for human information until the advent of the internet in the 1990s.
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television (TV), a form of mass media based on the electronic delivery of moving images and sound from a source to a receiver. By extending the senses of vision and hearing beyond the limits of physical distance, television has had a considerable influence on society. Conceived in the early 20th century as a possible medium for education and interpersonal communication, it became by mid-century a vibrant broadcast medium, using the model of broadcast radio to bring news and entertainment to people all over the world. Television is now delivered in a variety of ways: “over the air” by terrestrial radio waves (traditional broadcast TV); along coaxial cables (cable TV); reflected off of satellites held in geostationary Earth orbit (direct broadcast satellite, or DBS, TV); streamed through the Internet; and recorded optically on digital video discs (DVDs) and Blu-ray discs.
The technical standards for modern television, both monochrome (black-and-white) and colour, were first established in the middle of the 20th century. Improvements have been made continuously since that time, and television technology changed considerably in the early 21st century. Much attention was focused on increasing the picture resolution (high-definition television [HDTV]) and on changing the dimensions of the television receiver to show wide-screen pictures. In addition, the transmission of digitally encoded television signals was instituted to provide interactive service and to broadcast multiple programs in the channel space previously occupied by one program.
The dream of seeing distant places is as old as the human imagination. Priests in ancient Greece studied the entrails of birds, trying to see in them what the birds had seen when they flew over the horizon. They believed that their gods, sitting in comfort on Mount Olympus, were gifted with the ability to watch human activity all over the world. And the opening scene of William Shakespeare’s play Henry IV, Part 1 introduces the character Rumour, upon whom the other characters rely for news of what is happening in the far corners of England.
For ages it remained a dream, and then television came along, beginning with an accidental discovery. In 1872, while investigating materials for use in the transatlantic cable, English telegraph worker Joseph May realized that a selenium wire was varying in its electrical conductivity. Further investigation showed that the change occurred when a beam of sunlight fell on the wire, which by chance had been placed on a table near the window. Although its importance was not realized at the time, this happenstance provided the basis for changing light into an electric signal.
In 1880 a French engineer, Maurice LeBlanc, published an article in the journal La Lumière électrique that formed the basis of all subsequent television. LeBlanc proposed a scanning mechanism that would take advantage of the retina’s temporary but finite retainment of a visual image. He envisaged a photoelectric cell that would look upon only one portion at a time of the picture to be transmitted. Starting at the upper left corner of the picture, the cell would proceed to the right-hand side and then jump back to the left-hand side, only one line lower. It would continue in this way, transmitting information on how much light was seen at each portion, until the entire picture was scanned, in a manner similar to the eye reading a page of text. A receiver would be synchronized with the transmitter, reconstructing the original image line by line.
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The concept of scanning, which established the possibility of using only a single wire or channel for transmission of an entire image, became and remains to this day the basis of all television. LeBlanc, however, was never able to construct a working machine. Nor was the man who took television to the next stage: Paul Nipkow, a German engineer who invented the scanning disk. Nipkow’s 1884 patent for an Elektrisches Telescop was based on a simple rotating disk perforated with an inward-spiraling sequence of holes. It would be placed so that it blocked reflected light from the subject. As the disk rotated, the outermost hole would move across the scene, letting through light from the first “line” of the picture. The next hole would do the same thing slightly lower, and so on. One complete revolution of the disk would provide a complete picture, or “scan,” of the subject.
Jan 12, 2022 · Television is really a three-part invention: the TV camera that turns a picture and sound into a signal; the TV transmitter that sends the signal through the air; and the TV receiver (the TV set in your home) that captures the signal and turns it back into picture and sound.
Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, entertainment, news, and sports.
Jan 9, 2024 · Definition of Television and Radio. Television, often referred to as TV, is a telecommunication system for transmitting and receiving moving images and sound. It is a widely used medium for entertainment, news, advertising, and education.
Oct 8, 2024 · broadcasting, electronic transmission of radio and television signals that are intended for general public reception, as distinguished from private signals that are directed to specific receivers.
May 20, 2022 · Until the Internet came along, nothing could rival the reach of radio—not even television. A radio is a box filled with electronic components that catches radio waves sailing through the air, a bit like a baseball catcher's mitt, and converts them back into sounds your ears can hear.
