Television is a telecommunication medium which is used for transmitting and receiving moving images. It is either monochromatic (black and white) or colored and accompanied by sound. The closed-circuit television form is the most common medium used for broadband television. It uses high-powered radio-frequency transmitters to broadcast the signal to individual receivers. The broadcast is propagated through radio transmissions in the 7-1000 megahertz range of the FM frequency band. Earlier, the broadcast programs were recorded and transmitted as an analog signal, but in recent years commercial broadcasters have been progressively introducing digital broadcasting technology. Timeline of TV Sets The first television invented was a mechanical TV system based on the technology of rotating disks. Later, electronic systems were invented using the cathode ray tube (CRT). Paul Gottlieb Nipkow―Mechanical Television In 1884, Paul Nipkow, an engineering student from Germany proposed the world's first mechanical television system. He discovered the scanning principle in which light intensities of small portions of an image were successively analyzed and transmitted. He also devised the notion of dissecting the image and transmitting it sequentially. Later, he designed the first TV scanning device. Paul produced a rotating scanning disk camera called the Nipkow disk. This device was used for picture analysis and consisted of a rapidly rotating disk placed between a scene and a light-sensitive selenium element. The image generated by it had only 18 lines of resolution. Boris Rosing―Cathode Ray Tube Television In 1907, the Russian scientist Boris Rosing used a cathode ray tube (CRT) in the receiver of a television system, which at the camera end made use of mirror-drum scanning. He transmitted crude geometrical patterns onto the screen and was the first to do so using a CRT. John Baird―Mechanical Television During the 1920s, John Baird came up with the idea of using arrays of transparent rods to transmit images for television. His technology was based on Paul Nipkow's scanning disk idea, and had 30 line images which reflected light rather than backlit silhouettes. This created the first televised pictures of objects in motion (1924) and the human face (1925). In 1926, John televised the first moving object image at the Royal Institution in London, and by 1928 his transatlantic transmission of the image of a human face was a broadcasting milestone. In 1929, the British Broadcasting Company (BBC) started broadcasting on the Baird 30-line system, and in 1930, the first British play 'The Man with the Flower in his Mouth', having both sound and vision was televised. By 1936, the BBC adopted the electronic television technology of Marconi-EMI (the world's first regular high-resolution service having 405 lines per picture). Charles Francis Jenkins―Mechanical Television On June 14, 1923, Charles Jenkins invented a mechanical system called radiovision, which transmitted the earliest moving silhouettes. Radiovisor was a mechanical scanning-drum device manufactured by the Jenkins Television Corporation. It had a special attachment for receiving pictures, a cloudy 40 to 48 line image projected onto a six-inch square mirror. It was believed that watching a radiomovie required the viewer to constantly re-tune into the broadcast. Vladimir Kosma Zworykin―Electronic Television In 1929, Vladimir Zworykin, a Russian inventor, discovered the kinescope. Using the kinescope tube, he demonstrated a system with all the features of modern picture tubes. Later, he invented the iconoscope, a tube for television transmission which was earlier used in cameras. Philo T. Farnsworth―Electronic Television In 1927, Philo Farnsworth transmitted an image that comprised 60 horizontal lines. Later, he developed the dissector tube, the basis of all current electronic televisions. Louis W. Parker―Television Receiver In 1988, Louis W. Parker was initiated into the Inventors Hall of Fame for his invention of the intercarrier sound system for TV sets, which formed the modern basis for coordinating sound and picture in TV receivers. His system is now used in all receivers across the world. Color Television In 1904, a German patent held the first recorded proposal for a color television system. Later in 1925, Zworykin filed a patent for an all-electronic color television. However, both these systems were unsuccessful. On December 17, 1953, the first successful colored television system was broadcast commercially. It was based on the system designed by Radio Corporation of America (RCA) and authorized by Federal Communications Commission (FCC). Commercially available since the 1930s, television has become a popular communication medium for homes, businesses, institutions, and is a major source of news and entertainment. Since the 1970s, the availability of video cassettes, DVDs, discs has resulted in viewing recorded material on television sets.