Question: For how long did the channel airing Bagpuss alternate different broadcasting systems?

full_context: Document 1: Bagpuss: Bagpuss is a British children's television series, made by Peter Firmin and Oliver Postgate through their company Smallfilms. The series of 13 episodes was first broadcast from 12 February 1974 to 7 May 1974. The title character was "a saggy, old cloth cat, baggy, and a bit loose at the seams". Although only 13 episodes were made, it remains fondly remembered, and was frequently repeated in the UK for 13 years. In 1999 "Bagpuss" topped a BBC poll for the UK's favourite children's TV programme.
Document 2: High-definition television: Colour broadcasts started at similarly higher resolutions, first with the US NTSC color system in 1953, which was compatible with the earlier monochrome systems and therefore had the same 525 lines of resolution. European standards did not follow until the 1960s, when the PAL and SECAM color systems were added to the monochrome 625 line broadcasts.
Document 3: 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 4: Masha and the Bear: Masha and the Bear Russian Маша и Медведь Genre Adventure, comedy Created by Oleg Kuzovkov Country of origin Russia Original language (s) Russian No. of seasons No. of episodes 72 Production Running time 7 minutes Production company (s) Animaccord Animation Studio Distributor Animaccord Animation Studio Release Original network Russia 1, Carousel, Teletoon, Treehouse TV (Canada) Universal Kids (US) Spacetoon (Arab world) Cartoonito, Boomerang and Tiny Pop (UK) Cúla 4 (Ireland) PLUSPLUS (Ukraine) Original release 18 January 2009 (2009 - 01 - 18) -- present External links Website
Document 5: List of Peppa Pig episodes: Peppa Pig is a British preschool animated television series produced by Astley Baker Davies. The show features the eponymous pig along with her family and friends. Each episode is approximately five minutes long and there have been five seasons to date. Peppa Pig has been broadcast in over 180 countries.
Document 6: Wallace and Gromit: Wallace and Gromit is a British stop motion clay animation comedy series created by Nick Park of Aardman Animations. The series consists of four short films and one feature-length film, but has spawned numerous spin-offs and TV adaptations. The series centres on Wallace, a good-natured, eccentric, cheese-loving inventor, along with his companion Gromit, a silent yet loyal and intelligent anthropomorphic dog. The first short film, "A Grand Day Out", was finished and made public in the year 1989. Wallace was originally voiced by veteran actor Peter Sallis, and later by Ben Whitehead. Gromit always remains silent, instead communicating only through means of facial expressions and body language.
Document 7: Clangers: Clangers is a British stop - motion children's television series, comprising short films about a race (or perhaps a family) of creatures who live on, and inside, a small moon - like planet. They speak only in whistles, and eat only green soup (supplied by the Soup Dragon) and blue string pudding. The programmes were originally broadcast on BBC1 between 1969 and 1972, followed by a special episode which was broadcast in 1974.
Document 8: 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 9: 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 10: 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.
Document 11: Postcards from Buster: Postcards from Buster is a children's television series containing both animation and live-action that originally aired on PBS. It is a spin-off of the "Arthur" cartoon series. The show stars Arthur's best friend, 8-year-old rabbit Buster Baxter. Inspired by a 2003 episode of "Arthur" entitled "Postcards from Buster", the television series was created by Cookie Jar Group (now known as DHX Media), WGBH Boston and Marc Brown Studios.
Document 12: 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 13: 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 14: 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 15: Mr. Bean: Mr. Bean is a British sitcom created by Rowan Atkinson and Richard Curtis, produced by Tiger Aspect Productions and starring Atkinson as the title character. The sitcom consisted of 15 episodes that were co-written by Atkinson alongside Curtis and Robin Driscoll; for the pilot, it was co-written by Ben Elton. The series was originally broadcast on ITV, beginning with the pilot on 1 January 1990 and ending with "The Best Bits of Mr. Bean" on 15 December 1995. The fourteenth episode, "Hair by Mr. Bean of London", was not broadcast on television until 25 August 2006 on Nickelodeon.
ground_truth: six months
sub_queries: What channel aired Bagpuss? Answer: BBC
For how long did the BBC alternate different broadcasting systems? Answer: six months