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. In later electric phonographs (also known as record players (since 1940s) or, most recently, turntables), the motions of the stylus are converted into an analogous electrical signal by a transducer called a pickup or cartridge (colloquially called the "needle"), electronically amplified with a power amplifier, then converted back into sound by a loudspeaker.