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Edison gave a sketch of the machine to his mechanic, John Kruesi, to build, which Kruesi supposedly did within 30 hours. When one would speak into a mouthpiece, the sound vibrations would be indented onto the cylinder by the recording needle in a vertical (or hill and dale) groove pattern. The machine had two diaphragm-and-needle units, one for recording, and one for playback. Edison later changed the paper to a metal cylinder with tin foil wrapped around it. The speaking vibrations made indentations in the paper.
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He experimented with a diaphragm which had an embossing point and was held against rapidly-moving paraffin paper. This development led Edison to speculate that a telephone message could also be recorded in a similar fashion. In 1877, Edison was working on a machine that would transcribe telegraphic messages through indentations on paper tape, which could later be sent over the telegraph repeatedly. The phonograph was developed as a result of Thomas Edison's work on two other inventions, the telegraph and the telephone. Listen to this page History of the Cylinder Phonograph Phonograph Catalog/Advertisement:
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