FM standards. These tests were conducted by KDKA-FM in Pittsburgh, Pennsylvania during July and August 1960. In April 1961 the FCC adopted stereophonic FM technical standards, largely based on a Zenith-General Electric proposal, with licensed regular stereophonic FM radio broadcasting set to begin in the United States on June 1, 1961. At midnight in their respective time zones on June 1, General Electric's WGFM in Schenectady, New York, Zenith's WEFM in Chicago, and KMLA in Los Angeles became the first three stations to begin broadcasting using the new stereo standards. Following experimental FM stereo transmissions in the London area in 1958 and regular Saturday morning demonstration transmissions using TV sound and medium wave (AM) radio to provide the two channels, the first regular BBC transmissions using an FM stereo signal began on the BBC's Third Programme network on August 28, 1962. In Sweden, Televerket invented a different stereo broadcasting system called the Compander System. It had a high level of channel separation and could even be used to broadcast two separate mono signals for example for language studies (with two languages at the same time). But tuners and receivers with the pilot-tone system were sold so people in southern Sweden could listen to, for example, Danish radio. At last Sweden (the Televerket) decided to start broadcasting in stereo according to the pilot-tone system in 1977. AM standards For AM broadcasting very few stations transmit in stereo, in part due to the limited audio quality of the majority of receivers, and the scarcity of AM stereo receivers. Various modulation schemes are used for AM stereo, of which the best-known is Motorola's C-QUAM, the official method for most countries in the world that transmit in AM stereo. More AM stations are adopting digital HD Radio, which allows the transmission of stereo sound on AM stations; HD Radio's lack of compatibility with C-QUAM along with other interference issues has hindered HD Radio's use on the AM dial. For Digital Audio Broadcasting, MP2 audio streams are used. DAB is one of the Digital Radio formats that is used to broadcast Digital Audio over terrestrial broadcast networks or satellite networks. DAB is extended to video, and the new format is called DMB. Television A December 11, 1952 closed-circuit television performance of Carmen, from the Metropolitan Opera House in New York City to 31 theaters across the United States, included a stereophonic sound system developed by