Edison Phonograph

an instrument for mechanical sound recording and reproduction, invented by T. A. Edison in 1877. The sound is recorded by a needle on a cylinder wrapped with tin foil or on paper tape coated with a layer of wax; the needle is coupled to a diaphragm and traces a helical groove of variable depth on the surface of the foil. During reproduction, the needle moves along the groove and is mechanically vibrated, and the coupled diaphragm radiates sound. In an improved form the Edison phonograph was used until the 1930’s, mostly as a dictaphone. Later phonographs incorporating design improvements—disks instead of cyinders and electrical and magnetic recording—supplanted Edison’s original design in the 1940’s and 1950’s.