Question: How long did the distributor of Fascist Legacy alternate different broadcasting systems?

full_context: Document 1: Fascist Legacy: Fascist Legacy is a 1989 BBC documentary TV miniseries about Italian war crimes during World War II. It consists of two parts.
Document 2: Fallujah, The Hidden Massacre: Fallujah, The Hidden Massacre is a documentary film by Sigfrido Ranucci and Maurizio Torrealta which first aired on Italy's RAI state television network on November 8, 2005. The film documents the use of weapons that the documentary asserts are chemical weapons, particularly the use of incendiary bombs, and alleges indiscriminate use of violence against civilians and children by military forces of the United States of America in the city of Fallujah in Iraq during the Fallujah Offensive of November 2004.
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: Stefano Missio: He has made various documentaries among which "When Italy was not a poor country", about Italy in the 1960s narrated by Joris Ivens, and "Scusi, dov'è il Nord Est?" produced by Fandango and On Line Productions for Arte (broadcast as "Succes à l'italienne") and broadcast in Italy by Tele+. In 2005 he directed "Il Ponte", a fiction short-movie, screenplayed by Francesco Tullio Altan, starring Carlo Mazzacurati and Valentina Fago. His last work, Che Guevara - The body and the legend (2007), was broadcast in 12 different countries. He works and lives in Paris.
Document 5: 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 6: 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 7: 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 8: Ossessione: Visconti adapted the script with a group of men he selected from the Milanese magazine "Cinema". The members of this group were talented filmmakers and writers and played a large role in the emerging neorealist movement: Mario Alicata, Gianni Puccini, Antonio Pietrangeli and Giuseppe De Santis. When "Ossessione" was completed and released in 1943, it was far from the innocent murder mystery the authorities had expected; after a few screenings in Rome and northern Italy, prompting outraged reactions from Fascist and Church authorities, the film was banned by the Fascist government reestablished in the German occupied part of Italy after the September 1943 armistice. Eventually the Fascists destroyed the film, but Visconti managed to keep a duplicate negative from which all existing prints have been made. After the war, "Ossessione" encountered more problems with mass distribution, this time in the United States. As a result of the wartime production schedule, Visconti had never obtained the rights to the novel and Metro-Goldwyn Mayer began production on another version of the film, directed by Tay Garnett ("The Postman Always Rings Twice", 1946), while the Fascist ban on Visconti's work was still in effect.
Document 9: 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 10: Military history of Italy during World War II: However Italy's conquests were always heavily contested, both by various insurgencies (most prominently the Greek resistance and Yugoslav partisans) and Allied military forces, which waged the Battle of the Mediterranean throughout and beyond Italy's participation. Ultimately the Italian empire collapsed after disastrous defeats in the Eastern European and North African campaigns. In July 1943, following the Allied invasion of Sicily, Benito Mussolini was arrested by order of King Victor Emmanuel III, provoking a civil war. Italy's military outside of the peninsula itself collapsed, its occupied and annexed territories falling under German control. Italy surrendered to the Allies at the end of the Italian Campaign.
Document 11: The Death of Yugoslavia: The Death of Yugoslavia (broadcast as Yugoslavia: Death of a Nation in the US) is a BBC documentary series first broadcast in 1995, and it is also the title of a BBC book by Allan Little and Laura Silber that accompanies the series. It covers the collapse of Yugoslavia, the subsequent wars and the signing of the final peace accords. It uses a combination of archived footage interspersed with interviews with most of the main players in the conflict, including Slobodan Milošević, Radovan Karadžić, Franjo Tuđman and Alija Izetbegović, as well as members of the International political community, who were active in the various peace initiatives.
Document 12: 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 13: Military history of Italy during World War II: The participation of Italy in the Second World War was characterized by a complex framework of ideology, politics, and diplomacy, while its military actions were often heavily influenced by external factors. The imperial ambitions of the Fascist regime, which aspired to restore the Roman Empire in North Africa and the Mediterranean (the Mare Nostrum, or the Italian Empire), were partially met with the annexation of Albania and the Province of Ljubljana, and the occupation of British Somaliland and other territories, but ultimately collapsed after defeats in the East and North African campaigns. In July 1943, following the Allied invasion of Sicily, Benito Mussolini was arrested by order of King Victor Emmanuel III, provoking a civil war. Italy surrendered to the Allies at the end of the Italian Campaign. The northern half of the country was occupied by Germans with the fascists help and made a collaborationist puppet state (with more than 600,000 soldiers), while the south was governed by monarchist and liberal forces, which fought for the Allied cause as the Italian Co-Belligerent Army (at its height numbering more than 50,000 men), helped by circa 350,000 partisans of disparate political ideologies that operated all over Italy.
Document 14: 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 15: Albanian Fascist Party: The Albanian Fascist Party (, or PFSh) was a Fascist organization active during World War II which held nominal power in Albania from 1939, when the country was conquered by Italy, until 1943, when Italy capitulated to the Allies. Afterwards, Albania fell under German occupation, and the PFSh was replaced by the Guard of Greater Albania.
ground_truth: six months
sub_queries: Who distributed Fascist Legacy? Answer: BBC
For how long did the BBC alternate different broadcasting systems? Answer: six months