To give RCA a chance to establish itself, GE and Westinghouse were required to refrain from competing in the radio business for the next two and one-half years. Television RCA began television development in early 1929, after an overly optimistic Vladimir K. Zworykin convinced Sarnoff that a commercial version of his prototype system could be produced in a relatively short time for $100,000. Following what would actually be many years of additional research and millions of dollars, RCA demonstrated an all-electronic black-and-white television system at the 1939 New York World's Fair. RCA began regular experimental television broadcasting from the NBC studios to the New York metropolitan area on April 30, 1939, via station W2XBS, channel 1 (which evolved into WNBC channel 4) from the new Empire State Building transmitter on top of the structure. Around this time, RCA began selling its first television set models, including the TRK-5 and TRK-9, in various New York stores. However, the FCC had not approved the start of commercial television operations, because technical standards had not yet been finalized. Concerned that RCA's broadcasts were an attempt to flood the market with sets that would force it to adopt RCA's current technology, the FCC stepped in to limit its broadcasts. Following the adoption of National Television System Committee (NTSC) recommended standards, the FCC authorized the start of commercial television broadcasts on July 1, 1941. The entry of the United States into World War II a few months later greatly slowed its deployment, but RCA resumed selling television receivers almost immediately after the war ended in 1945. In 1950, the FCC adopted a standard for color television that had been promoted by CBS, but the effort soon failed, primarily because the color broadcasts could not be received by existing black-and-white sets. As the result of a major research push, RCA engineers developed a method of "compatible" color transmissions that, through the use of interlacing, simultaneously broadcast color and black-and-white images, which could be picked up by both color and existing black-and-white sets. In 1953, RCA's all-electronic color television technology was adopted as the standard for the United States. At that time, Sarnoff predicted annual color television sales would reach 1.78 million in 1956, but the receivers were expensive and difficult to adjust, and there was initially a lack of color programming, so sales lagged badly and the actual 1956 total would only be 120,000. RCA's ownership