Phonograph
Edison created the phonograph in a single day in 1877. But behind this invention was years of experiences, which he could call back and relate to each other to develop an entirely new idea.
At the age of seventeen, Edison had worked as a telegraphist. There he had invented a simple Morse-signal recording apparatus, which consisted of paper disc which would rotate on its axis while the incoming dots and dashes would be indented on it.
Eleven years later, working in his own laboratory, he improved this invention so that a similar disc - with the message indented in dots and dashes - could be used also for sending messages. This gadget was for the sole purpose of receiving and sending electrical impulses, and had nothing to do with recording and producing sounds. However, Edison noticed that it often did accidentally produce a hum, specially when the disc rotated fast enough.
It was this observation which led Edison to invent the phonograph. All he had to do was to substitute the paper disc with a cylinder covered with soft tin foil, and to attach the needle to a membrane which would vibrate by the sound waves. The total investment for this invention worked out to just eighteen dollars and thirty hours.
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