One of the earliest proposals for a mechanical television system was put forward by German researcher Paul Nipkow in 1883. When he developed patent No. 30,105, he was an unknown twenty-three-year-old student living in Berlin. It proved to be the basis for most early television schemes in the world, although he never built the apparatus.
In Nipkow's patent, which he called an 'electric telescope', a disc was
punched with holes in a spiral near the outer edge. When the disc
revolved, each hole vertically scanned a line of the image, allowing
variations in light to reach a selenium cell. As one hole swept over a
segment of the picture, the next in sequence tackled the portion next to
it, until the complete subject had been scanned. The selenium cell
transferred the light variations to an electronic signal. Pictures were
reconstituted at the receiver by a similar disc which was synchronized
with the transmitter.
For further detail, see How Mechanical TV Works.
Charles F. Jenkins (1867 - 1934)
One of the better known experimenters with mechanical television was Charles Francis Jenkins, a prolific American inventor. In May 1920, at the Toronto meeting of the Society of Motion Picture Engineers, Jenkins introduced his "prismatic rings" as a device to replace the shutter on a film projector. This invention laid the foundation for his first radiovision broadcast. He claimed to have transmitted the earliest moving silhouette images on June 14, 1923, but his first public demonstration of these did not take place until June of 1925.
Jenkins Laboratories constructed a radiovision transmitter, W3XK, in Washington D.C. The short-wave station began transmitting radiomovies across the Eastern U.S. on a regular basis by July 2, 1928. Jenkins wrote in 1929: "This gave the amateur action-pictures to "fish" for; and during August following a hundred or more had finished their receivers and were dependably getting our broadcast pictures, and reporting thereon, to our great help." It was in this way that Jenkins actively promoted enthusiasm and experimentation in the short-wave radio community, and the U.S. experienced its first television boom, with an estimated 20,000 lookers-in.
John Logie Baird (1888 - 1946)
John Logie Baird, a Scottish engineer and entrepreneur, achieved his first transmissions of simple face shapes in 1924 using mechanical television. On March 25, 1925, Baird held his first public demonstration of "television" at the London department store Selfridges on Oxford Street in London. In this demonstration, he had not yet obtained adequate half-tones in the moving pictures, and only silhouettes were visible.
In the first week of October, 1925, Baird obtained the first actual television picture in his laboratory. At this time, his test subject was a ventriloquist's dummy, "Stooky Bill" which was placed in front of the camera apparatus. Baird later recollected, "The image of the dummy's head formed itself on the screen with what appeared to me an almost unbelievable clarity. I had got it! I could scarcely believe my eyes and felt myself shaking with excitement".
After much discussion with his business associates, and further improvements, Baird decided to publicly demonstrate television on Tuesday 26 January, 1926, again at Selfridge's department store. This was the first opportunity for the general public to see television. The Baird company continued to publicize this historic demonstration, and J.L. Baird's other scientific breakthroughs as they feverishly worked to obtain financial backing and construct a line of home receivers.
With Baird's transmitting equipment, the British Broadcasting Corporation began regular experimental television broadcasts on September 30, 1929. By the following year, most of Britain's major radio dealers were selling Baird kits and ready-made receivers through retail and by mail order.
More about Baird
Allen B. DuMont (1901-1965)
DuMont was a brilliant inventor, television manufacturer and broadcaster. DuMont had been chief engineer of the De Forest Radio Company until 1931. After resigning as Chief Engineer of the De Forest Radio Company in 1931, he started his own company which, among other electronic accomplishments, developed better cathode-ray tubes, improving the picture size, reliability and operating life of what became the television picture tube.
In 1938, Paramount Pictures invested in the firm, allowing DuMont to expand its television research and begin manufacturing receivers and broadcasting TV programs. Allen B. DuMont Laboratories became a major source of competition for RCA, offering a set with a 14" screen in 1938, while RCA was only able to release a 12" set a few months later. Du Mont appeared frequently before the FCC, opposing the CBS field-sequential colour system and later, the mix of VHF and UHF channels in the same broadcast areas.
Immediately after World War II, DuMont took the lead in developing larger and larger direct-view tubes (up to 30" in size). Many of the favourite shows of the late forties and early fifties appeared on DuMont's television network, such as Jackie Gleason, Ted Mack's Amateur Hour, and Bishop Sheen appeared on DuMont's television network. The "fourth network" went off the air in 1955.
Philo T. Farnsworth (1906-1971)
A remarkable inventor, Utah-born Philo T. Farnsworth developed the world's first all-electronic system of television in 1927 at the age of 21! He publically demonstrated the first all-electronic television image in September, 1928.
Like John Logie Baird, the pioneer of mechanical television, the young inventor had difficulty obtaining financing for his experiments. By 1929, Farnsworth's shareholders insisted that his television system be shown to RCA. Initially, RCA decided that it could do without Farnsworth's television camera patents, but elements of his "Image Dissector" camera pick-up tube became essential to making RCA's (Zworykin's) television camera, the "Iconoscope", work properly.
Patent litigation between RCA and Farnsworth Television and Radio Corporation became intense. RCA tried to buy out Farnsworth, but he preferred a share of the profits. Finally, in September1939 a cross-licensing agreement was reached, and electronic television could "begin" in North America. Both companies were able to operate their systems successfully prior to this date, however camera-related problems persisted until RCA introduced a better "Image Orthicon" after World War II.
After television, Farnsworth became involved in radar and atomic energy research. In the last few years, his television accomplishments have been increasingly recognized by historians.
David Sarnoff (1891-1971)
Sarnoff first gained fame in 1912 during the Titanic disaster, as the telegraph operator who received the transmissions of survivors' names (a legend some historians now regard as myth). In the "Music Box Memo" of 1915, which he sent to his employer, the Marconi Company of America, Sarnoff recognized the potential of organized radio broadcasting to stimulate receiver sales. This concept led to his promotion to vice-president of RCA.
As President of the Radio Corporation of America (RCA) during the 30's and 40's, he was instrumental in financing the development of electronic television. He founded NBC, the radio broadcasting arm of RCA, in 1926. NBC facilitated some of the earliest American mechanical television broadcasts in 1928 with experimental transmissions of Felix the cat. Meanwhile, Sarnoff encouraged Zworykin to continue to develop an all-electronic television system.
Under Sarnoff's direction, RCA spent over thirteen million dollars from 1930 to 1939 to develop television, which was a staggering sum during the Depression. RCA also engaged in patent litigation with Farnsworth Television and Radio Corporation, which held key television patents. It was alleged that the Federal Radio Commission was being manipulated by the RCA cartel of companies. Purchasing of key Patents ensured RCA's dominance of radio and television technology, but simultaneously helped to finance and encourage continued television experimenation outside RCA. Sarnoff's determination ensured that RCA was the company to bring television to the American public. Without Sarnoff's prophetic vision, widely available commercial television would certainly have been substantially different.
Vladimir K. Zworykin (1889-1982)
Zworykin developed some of the most important electronic TV camera and receiver technologies. While he was a student in Russia, Zworykin had the good fortune to study under Boris Rosing, an early cathode-ray tube experimenter. Zworykin immigrated to the U.S. in 1919, after the Bolshevik revolution. He began research on his "Iconoscope" (an early electronic camera tube) which he patented in 1923.
While an employee at Westinghouse, one of Zworykin's superiors discovered that he was researching television, and his supervisor was told to put Zworykin to work on "something more useful." Over the next 6 years, he continued research in photoelectric and receiving tubes, and on November 18, 1929, Zworykin demonstrated his all-electronic television receiver using a "Kinescope" (picture tube).
At David Sarnoff's invitation, Zworykin came to work for RCA, where he directed all of the television research, particularly that which led up to RCA's introduction of television at the New York World's Fair. Zworykin retired as Director of Electronics Research for RCA in 1954, and continued his work as a consultant.