|Improvement in Telegraphic Apparatus
||The pantelegraph is a system of sending and receiving images over long distances by means of telegraph wiring. This system was actually the first prototype of a fax machine that was commercially exploited, though the images transmitted by telegraph were reproduced using electrochemistry rather than optical image scanning of the fax machine. The technology is relatively simple. An image is made using non-conductive ink on a piece of tin foil. A stylus, that is in the electrical circuit of the tin foil, is then passed over the foil where it lightly touches it. The stylus passes with parallel scans slightly apart. Electricity conducts where there is no ink and does not where there is ink. This causes on and off circuits matching the image as it scans. The signals are then sent along a long distance telegraph line. The receiver at the other end has an electrical stylus and scans blue dye ink on white paper reproducing the image line-by-line, a fac simile (Latin, "make similar") of the original image.
||February 3, 1863
|Elektrisches Teleskop (German)
||21 (old German)
||The first electromechanical television system which employed a scanning disk, a spinning disk with a series of holes spiraling toward the center, for rasterization. The holes were spaced at equal angular intervals such that in a single rotation the disk would allow light to pass through each hole and onto a light-sensitive selenium sensor which produced the electrical pulses. As an image was focused on the rotating disk, each hole captured a horizontal "slice" of the whole image. Nipkow's design would not be practical until advances in amplifier tube technology became available. The device was only useful for transmitting still "halftone" images — represented by equally spaced dots of varying size — over telegraph or telephone lines.
||January 6, 1884
|Apparatus for transmitting views or images to a distance
||Electromechanical grayscale TV system, using mechanical picture scanning in the form of a scanning disk , with electronic amplification at the transmitter and at the receiver. Because only a limited number of holes could be made in the disks, and disks beyond a certain diameter became impractical, image resolution on mechanical television broadcasts was typically very low, ranging from about 30 lines up to 120.
||John Logie Baird
||Television Limited, London
||January 15, 1929
||The image dissector tube; a video camera tube, the basis of current electronic televisions. When light emitted from an object strikes, through lens. a plate coated with cessium oxide, the palate emits electrons according to the light strength. This stream of electrons is detected, amplified and transmitted to a television receiver. Farnsworth submitted the patent application for the image dissector on January 7, 1927. On September 7 of that year, the image dissector successfully transmitted its first image, a simple straight line, at Farnsworth's laboratory at 202 Green Street in San Francisco. By September 3, 1928, Farnsworth had developed the system sufficiently to hold a demonstration for the press, the first such successful demonstration of a fully electronic television system.
||Philo T. Farnsworth
||Television Laboratories, Inc., San Francisco
||August 26, 1930
|Television apparatus and the like
||The world's first working color television system, though mechanical. Using synchronized scanning discs at the transmitting and receiving ends. The transmitting station consists of sensitive light cells differing in their sensitivity to different light colors. The receiving station comprises lamps adapted to emit light corresponding in colour to each cell colour sensitivity. Baird also made the world's first color broadcast on February 4, 1938, sending a mechanically scanned 120-line image from Baird's Crystal Palace studios to a projection screen at London's Dominion Theatre.
||John Logie Baird
||Television Limited, London
||September 5, 1933
||The Iconoscope, an early television camera tube. Within the iconoscope, an image was projected onto a plate containing a mosaic of electrically isolated photosensitive granules separated from a common plate by a thin layer of isolating material, each granule constituting a tiny capacitor with the common plate that accumulated and stored electrical charge in response to the light striking it. Emission of photoelectrons from each granule in proportion to the amount of light received resulted in a charge image being formed on the mosaic. An electron beam was then swept across the image plate from an electron gun, effectively scanning the stored image and discharging each capacitor in turn such that the electrical output from each capacitor was proportional to the average intensity of the light striking it between each discharge event. The Iconoscope was the leading camera tube used for broadcasting in the United States from 1936 until 1946, when it was replaced by the image orthicon tube.
||Vladimir K. Zworykin
||Westinghouse Electric & Manufacturing Company (1886), Pittsburgh, PA
||December 20, 1938