Film Technology . AGA became involved in film technology at an early stage. In 1919 AGA began manufacturing a hand-wound projector for silent movies. The source of light was an incandescent mantle which burned acetylene gas. The projector had a three-blade shutter for sixteen pictures. Back in 1912 Gustaf Dalén supported the Swedish engineer Sven Berglund's sound film experiments based on photographic registration of the sound on the film. However amplifier technology was so underdeveloped that these experiments did not provide any practical results. When the time eventually came when movie theaters needed to have sound systems, it was appropriate for AGA to start manufacturing this equipment. Since foreign projectors were too expensive, the Swedish Film Industry (SF) asked AGA at the end of the 1920s to start manufacturing sound film equipment. The first systems were delivered to a Stockholm movie theater in 1929. AGA-Baltic started by manufacturing a turntable for gramophone records where the sound was played-back synchronously with the film. 1931 saw the start of photographic registration of sound directly on the film. Sound playback took place in a so-called tone unit. AGA's design was so perfect that it was even used as a model in some places abroad.