Phonograph
From ETHW
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Menlo Park, New Jersey. Using ideas he mentioned in a patent for telephony improvements filed on 30 July 1877 (the recording of sound by transverse indentations in a v-shaped groove in a paper tape or on a sheet of tinfoil wrapped on a cylinder), Edison drew a sketch for the phonograph on 29 November 1877 that was used to make a working model a few days later. The device was demonstrated to Scientific American on Dec. 7. Edison filed for a patent on Dec 15th. And the invention was announced publicly in Scientific American on Dec. 22nd.
