Television is a system for reproducing images on a screen, usually transmitted in the form of radio waves. The development of television receivers from the late 19th Century made the concept of television possible, but it was not until the twentieth century that the technology was sophisticated enough to provide for the use of television as a mass entertainment medium.
The illusion of a moving image is caused by the fact that the eye is not sensitive enough to register very fast changes. The television operates by rapidly refreshing the image one line at a time, a process known as scanning. This process occurs so rapidly that the eye can not detect it, with the entire screen being refreshed many time per second. It is the basis of all television systems that have been developed.
The first mechanical television system was patented 1884 by German Paul Nipkow. Nipkow’s system involved a rotating disk into which holes had been punched in a spiral pattern. Light passing through the hole would land on a sample of selenium, a chemical element whose resistance changes when light is shone on it. The selenium was connected by wire to a lamp, which flickered as the resistance, and thus the electrical current in the circuit, changed. A disk at the other end of the apparatus would spin at the same rate as the original, and would project the original image onto a screen. This system had a very low resolution, with only 18 lines from the top to the bottom of the screen, and it is unknown whether a prototype of this device was ever constructed. However, it was the basis for later mechanical television systems developed by John Logie Baird in the UK, and Charles Jenkins in the USA.
The main problem with Nipkow’s system is that it was limited to being transmitted through wires. However, developments in physics were able to change that. In 1886 Heinrich Hertz proved the existence of radio waves, a concept first predicted in the 1860’s by Scottish physicist James Maxwell. Shortly afterwards, in 1895, Guglielmo Marconi transmitted one of the first radio signals, and by 1902 had transmitted the letter S in morse code across the Atlantic. Lee De Forest’s invention of the audion, a three electrode vacuum tube that amplified the radio waves, permitted sound and music to be transmitted with little interference.
The main pioneer of television in the UK was John Logie Baird. His television was based on the mechanical principles of the Nipkow disk, although had a 30 line resolution as opposed to the 18 lines of the original Nipkow system. In 1925 he gave the first public demonstration of the device. In 1928 he managed to broadcast the image of a face across the Atlantic, and by doing so gained the attention of the British Broadcasting Corporation, which began television transmissions in 1929.
Sections to addOther sections to write:
Cathode Ray Tube + electronic television
The move to colour: US: CBS + NTSC standards.
PAL/SECAM/NTSC etc standards.
Sound - mono, stereo (Nicam etc.), AC-3
Digital TV, ATSC, HDTV, Dolby AC-3, MPEG compression.
Brief mention of DVD, VHS, storage systems.
Channels: Descriptions of licensing requirements, UK, US.
Description of main networks, and history.
BBC, ITV network, Ch 4, 5, + US networks: CBS, PBS, NBC, ABC etc.
If it looks like I have missed anything, thats what the conversation is for!
Original Guide entry on which this is based
Television or T.V, as it has grown to be called is an ingenius idea and was invented in 1925 by a incredibly intellegent man named John Logie Baird. His research was based mainly on earlier works by people such as Willoughby Smith and Vladimir Zwyorkin. Their combined research led to regular broadcasting in Germany in 1935. The picture however was very poor. The BBC chose Baird's idea and became the first high-quality black-and-white broadcasting company in 1937. shortly afterwards, in 1938 Baird patented a photo-mechanical colour television system but his works were not viable untill 1953, when the USA came up with a standardized electronic system compatible with existing black-and-white receivers.This system, known as the NSTC system, is currently used in the USA and Japan. Elsewhere two other systems--SECAM (used in France and the Soviet Union) and PAL (used by most of Europe)--have been developed. More recent developments in television technology include the growth of cable television; the introduction of stereo sound; and satellite television, in which microwave transmissions are broadcast via communications satellites either directly to domestic satellite dishes, or to ground stations for relay via cable. . The increased bandwidth of satellite and cable systems has led to tens of television channels often being available to viewers. New developments include high-definition television (HDTV) broadcasting, in which the television images are made up of over 1,000 scanning lines instead of the current 525 or 625, and the transmission of television pictures as digital rather than analog signals. Japanese analog HDTV (Hi-Vision) television receivers were first sold in 1990. Television has now become the most important of the entertainment mass media today.