<P> On September 7, 1927, Farnsworth's image dissector camera tube transmitted its first image, a simple straight line, to a receiver in another room of his laboratory at 202 Green Street in San Francisco . Pem Farnsworth recalled in 1985 that her husband broke the stunned silence of his lab assistants by saying, "There you are--electronic television!" The source of the image was a glass slide, backlit by an arc lamp . An extremely bright source was required because of the low light sensitivity of the design . By 1928, Farnsworth had developed the system sufficiently to hold a demonstration for the press . His backers had demanded to know when they would see dollars from the invention; so the first image shown was, appropriately, a dollar sign . In 1929, the design was further improved by elimination of a motor - generator; so the television system now had no mechanical parts . That year Farnsworth transmitted the first live human images using his television system, including a three and a half - inch image of his wife Pem . </P> <P> Many inventors had built electromechanical television systems before Farnsworth's seminal contribution, but Farnsworth designed and built the world's first working all - electronic television system, employing electronic scanning in both the pickup and display devices . He first demonstrated his system to the press on September 3, 1928, and to the public at the Franklin Institute in Philadelphia on August 25, 1934 . </P> <P> In 1930, Vladimir Zworykin, who had been developing his own all - electronic television system at Westinghouse in Pittsburgh since 1923, but which he had never been able to make work or satisfactorily demonstrate to his superiors, was recruited by RCA to lead its television development department . Before leaving his old employer, Zworykin visited Farnsworth's laboratory and was sufficiently impressed with the performance of the Image Dissector that he reportedly had his team at Westinghouse make several copies of the device for experimentation . But Zworykin later abandoned research on the Image Dissector, which at the time required extremely bright illumination of its subjects to be effective, and turned his attention to what would become the Iconoscope . In a 1970s series of videotaped interviews, Zworykin recalled that, "Farnsworth was closer to this thing you're using now (i.e., a video camera) than anybody, because he used the cathode - ray tube for transmission . But, Farnsworth didn't have the mosaic (of discrete light elements), he didn't have storage . Therefore, (picture) definition was very low...But he was very proud, and he stuck to his method ." Contrary to Zworykin's statement, Farnsworth's patent #2,087,683 for the Image Dissector (filed April 26, 1933) features the "charge storage plate" invented by Tihanyi in 1928 and a "low velocity" method of electron scanning, also describes "discrete particles" whose "potential" is manipulated and "saturated" to varying degrees depending on their velocity . Farnsworth's patent numbers 2,140,695 and 2,233,888 are for a "charge storage dissector" and "charge storage amplifier," respectively . </P> <P> In 1931, David Sarnoff of RCA offered to buy Farnsworth's patents for US $100,000, with the stipulation that he become an employee of RCA, but Farnsworth refused . In June of that year, Farnsworth joined the Philco company and moved to Philadelphia along with his wife and two children . RCA would later file an interference suit against Farnsworth, claiming Zworykin's 1923 patent had priority over Farnsworth's design, despite the fact it could present no evidence that Zworykin had actually produced a functioning transmitter tube before 1931 . Farnsworth had lost two interference claims to Zworykin in 1928, but this time he prevailed and the U.S. Patent Office rendered a decision in 1934 awarding priority of the invention of the image dissector to Farnsworth . RCA lost a subsequent appeal, but litigation over a variety of issues continued for several years with Sarnoff finally agreeing to pay Farnsworth royalties . Zworykin received a patent in 1928 for a color transmission version of his 1923 patent application; he also divided his original application in 1931, receiving a patent in 1935, while a second one was eventually issued in 1938 by the Court of Appeals on a non-Farnsworth - related interference case, and over the objection of the Patent Office . </P>

According to postman what technology is a forerunner of television