A turntable is the circular rotating platform of a phonograph (a.k.a. record player, gramophone, turntable, etc.), a device for playing sound recordings. The phonograph is a device invented in 1877 for the mechanical recording and reproduction of sound. In its later forms it is also called a gramophone (as a trademark since 1887, as a generic name since c. 1900). The sound vibration waveforms are recorded as corresponding physical deviations of a spiral groove engraved, etched, incised, or impressed into the surface of a rotating cylinder or disc, called a "record". To recreate the sound, the surface is similarly rotated while a playback stylus traces the groove and is therefore vibrated by it, very faintly reproducing the recorded sound. In early acoustic phonographs, the stylus vibrated a diaphragm which produced sound waves which were coupled to the open air through a flaring horn, or directly to the listener's ears through stethoscope-type earphones.