Question: For how long did the receiver of most premier League matches alternate different broadcasting systems?

full_context: Document 1: BBC Television: After a series of test transmissions and special broadcasts that began in August, regular BBC television broadcasts officially resumed on 1 October 1936, from a converted wing of Alexandra Palace in London, which housed two studios, various scenery stores, make-up areas, dressing rooms, offices, and the transmitter itself, now broadcasting on the VHF band. BBC television initially used two systems, on alternate weeks: the 240-line Baird intermediate film system and the 405-line Marconi-EMI system, each making the BBC the world's first regular high-definition television service, broadcasting Monday to Saturday from 15:00 to 16:00 and 21:00 to 22:00.
Document 2: Premier League: The TV rights agreement between the Premier League and Sky has faced accusations of being a cartel, and a number of court cases have arisen as a result. An investigation by the Office of Fair Trading in 2002 found BSkyB to be dominant within the pay TV sports market, but concluded that there were insufficient grounds for the claim that BSkyB had abused its dominant position. In July 1999 the Premier League's method of selling rights collectively for all member clubs was investigated by the UK Restrictive Practices Court, who concluded that the agreement was not contrary to the public interest.
Document 3: BBC Television: After a series of test transmissions and special broadcasts that began in August 1936, the BBC Television Service officially launched on 2 November 1936 from a converted wing of Alexandra Palace in London. ``Ally Pally ''housed two studios, various scenery stores, make - up areas, dressing rooms, offices, and the transmitter itself, which then broadcast on the VHF band. BBC television initially used two systems on alternate weeks: the 240 - line Baird intermediate film system and the 405 - line Marconi - EMI system. The use of both formats made the BBC's service the world's first regular high - definition television service; it broadcast from Monday to Saturday between 15: 00 and 16: 00, and 21: 00 and 22: 00. The first programme broadcast -- and thus the first ever, on a dedicated TV channel -- was`` Opening of the BBC Television Service'' at 15: 00. The first major outside broadcast was the coronation of King George VI and Queen Elizabeth in May 1937.
Document 4: BBC Television: Mechanically scanned, 30-line television broadcasts by John Logie Baird began in 1929, using the BBC transmitter in London, and by 1930 a regular schedule of programmes was transmitted from the BBC antenna in Brookmans Park. Television production was switched from Baird's company to what is now known as BBC One on 2 August 1932, and continued until September 1935. Regularly scheduled electronically scanned television began from Alexandra Palace in London on 2 November 1936, to just a few hundred viewers in the immediate area. The first programme broadcast – and thus the first ever, on a dedicated TV channel – was "Opening of the BBC Television Service" at 15:00. The first major outside broadcast was the coronation of King George VI and Queen Elizabeth in May 1937. The service was reaching an estimated 25,000–40,000 homes before the outbreak of World War II which caused the service to be suspended in September 1939. The VHF broadcasts would have provided an ideal radio beacon for German bombers homing in on London, and the engineers and technicians of the service would be needed for the war effort, in particular the radar programme.
Document 5: Premier League: Television has played a major role in the history of the Premier League. The League's decision to assign broadcasting rights to BSkyB in 1992 was at the time a radical decision, but one that has paid off. At the time pay television was an almost untested proposition in the UK market, as was charging fans to watch live televised football. However, a combination of Sky's strategy, the quality of Premier League football and the public's appetite for the game has seen the value of the Premier League's TV rights soar.
Document 6: Sky UK: In the autumn of 1991, talks were held for the broadcast rights for Premier League for a five-year period, from the 1992 season. ITV were the current rights holders, and fought hard to retain the new rights. ITV had increased its offer from £18m to £34m per year to keep control of the rights. BSkyB joined forces with the BBC to make a counter bid. The BBC was given the highlights of most of the matches, while BSkyB paying £304m for the Premier League rights, would give them a monopoly of all live matches, up to 60 per year from the 1992 season.  Murdoch described sport as a "battering ram" for pay-television, providing a strong customer base. A few weeks after the deal, ITV went to the High Court to get an injunction as it believed their bid details had been leaked before the decision was taken. ITV also asked the Office of Fair Trading to investigate since it believed Rupert Murdoch's media empire via its newspapers had influenced the deal. A few days later neither action took effect, ITV believed BSkyB was telephoned and informed of its £262m bid, and Premier League advised BSkyB to increase its counter bid.
Document 7: Sky UK: While BSkyB had been excluded from being a part of the ONdigital consortium, thereby making them a competitor by default, BSkyB was able to join ITV Digital's free-to-air replacement, Freeview, in which it holds an equal stake with the BBC, ITV, Channel 4 and National Grid Wireless. Prior to October 2005, three BSkyB channels were available on this platform: Sky News, Sky Three, and Sky Sports News. Initially BSkyB provided Sky Travel to the service. However, this was replaced by Sky Three on 31 October 2005, which was itself later re-branded as 'Pick TV' in 2011.
Document 8: FA Cup: Many[who?] expected BSkyB to make a bid to show some of the remaining FA Cup games for the remainder of the 2009–10 season which would include a semi-final and shared rights to the final. ESPN took over the package Setanta held for the FA Cup from the 2010–11 season. The 2011 final was also shown live on Sky 3D in addition to ESPN (who provided the 3D coverage for Sky 3D) and ITV. Following the sale of ESPN's UK and Ireland channels to BT, ESPN's rights package transferred to BT Sport from the 2013–14 season.
Document 9: BBC Television: The two systems were to run on a trial basis for six months; early television sets supported both resolutions. However, the Baird system, which used a mechanical camera for filmed programming and Farnsworth image dissector cameras for live programming, proved too cumbersome and visually inferior, and ended with closedown (at 22:00) on Saturday 13 February 1937.
Document 10: Color television: After a series of hearings beginning in September 1949, the FCC found the RCA and CTI systems fraught with technical problems, inaccurate color reproduction, and expensive equipment, and so formally approved the CBS system as the U.S. color broadcasting standard on October 11, 1950. An unsuccessful lawsuit by RCA delayed the first commercial network broadcast in color until June 25, 1951, when a musical variety special titled simply Premiere was shown over a network of five East Coast CBS affiliates. Viewing was again restricted: the program could not be seen on black - and - white sets, and Variety estimated that only thirty prototype color receivers were available in the New York area. Regular color broadcasts began that same week with the daytime series The World Is Yours and Modern Homemakers.
Document 11: Premier League: At the close of the 1991 season, a proposal was tabled for the establishment of a new league that would bring more money into the game overall. The Founder Members Agreement, signed on 17 July 1991 by the game's top-flight clubs, established the basic principles for setting up the FA Premier League. The newly formed top division would have commercial independence from The Football Association and the Football League, giving the FA Premier League licence to negotiate its own broadcast and sponsorship agreements. The argument given at the time was that the extra income would allow English clubs to compete with teams across Europe.
Document 12: BBC Television: Baird Television Ltd. made Britain's first television broadcast, on 30 September 1929 from its studio in Long Acre, London, via the BBC's London transmitter, using the electromechanical system pioneered by John Logie Baird. This system used a vertically-scanned image of 30 lines – just enough resolution for a close-up of one person, and with a bandwidth low enough to use existing radio transmitters. Simultaneous transmission of sound and picture was achieved on 30 March 1930, by using the BBC's new twin transmitter at Brookmans Park. By late 1930, 30 minutes of morning programmes were broadcast Monday to Friday, and 30 minutes at midnight on Tuesdays and Fridays, after BBC radio went off the air. Baird broadcasts via the BBC continued until June 1932.
Document 13: Premier League: The managing director of London Weekend Television (LWT), Greg Dyke, met with the representatives of the "big five" football clubs in England in 1990. The meeting was to pave the way for a break away from The Football League. Dyke believed that it would be more lucrative for LWT if only the larger clubs in the country were featured on national television and wanted to establish whether the clubs would be interested in a larger share of television rights money. The five clubs decided it was a good idea and decided to press ahead with it; however, the league would have no credibility without the backing of The Football Association and so David Dein of Arsenal held talks to see whether the FA were receptive to the idea. The FA did not enjoy an amicable relationship with the Football League at the time and considered it as a way to weaken the Football League's position.
Document 14: Premier League: Television money had also become much more important; the Football League received £6.3 million for a two-year agreement in 1986, but when that deal was renewed in 1988, the price rose to £44 million over four years. The 1988 negotiations were the first signs of a breakaway league; ten clubs threatened to leave and form a "super league", but were eventually persuaded to stay. As stadiums improved and match attendance and revenues rose, the country's top teams again considered leaving the Football League in order to capitalise on the growing influx of money being pumped into the sport.
Document 15: High-definition television: Since the formal adoption of digital video broadcasting's (DVB) widescreen HDTV transmission modes in the early 2000s; the 525-line NTSC (and PAL-M) systems, as well as the European 625-line PAL and SECAM systems, are now regarded as standard definition television systems.
ground_truth: six months
sub_queries: Who was given the highlights of most of the matches? Answer: BBC
For how long did the BBC alternate different broadcasting systems? Answer: six months