LYCOS RETRIEVER 
Phonograph
built 633 days ago
A monaural phonograph record makes use of a spiral 90° V-shaped groove impressed into a plastic disc. As the record revolves at 33 rotations per minute, a tiny “needle,” or stylus, simultaneously moves along the groove and vibrates back and forth parallel to the surface of the disc and perpendicular to the groove, tracing out the sound wave.
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Disc Phonograph