A master-slave flip-flop circuit comprises a master stage for retaining a master signal, a slave stage for retaining a slave signal and a retention stage. The transmission includes a first member moveably connected to the first guideway and the second guideway, the first member includes gear teeth and a second member having gear teeth positioned at an adjustable angle relative to the first member. The blower housing can also be moved to a third repair position in which components thereof are accessible from the cab side of the sweeper. The flammable gas flowed out from the flammable-gas flow outlet is burnt with oxygen in exhaust gas to produce combustion heat. The information could be presented on a screen, printed on paper, etc.