record player or phonograph, device for reproducing sound that has been recorded as a spiral, undulating groove on a disk. This disk is known as a phonograph record, or simply a record (see sound recording). In using a record player, a record is placed on the player's motor-driven turntable, which rotates the record at a constant speed. A tone arm, containing a pickup at one end, is placed on the record. The tone arm touches the groove of the record with its stylus, or needle. As the record revolves, the variations in its groove cause the stylus to vibrate. The stylus is part of the pickup, a device that also contains a transducer to convert these mechanical vibrations into corresponding electrical signals. These signals are then increased in size by an amplifier. After leaving the amplifier, they are passed to a loudspeaker that converts them into sound.

Although sound waves had been recorded in the middle of the 19th cent., the first machine to reproduce recorded sound, the phonograph, was built by Thomas A. Edison in 1877. Edison's records were made of tinfoil, upon which a groove of unvarying lateral direction but varying depth was cut; later this method became known as "hill-and-dale" recording. In 1887, Emile Berliner invented the disk record (patented 1896), which has grooves of unvarying depth but of varying lateral direction. His method, called lateral recording, superseded the earlier method. Berliner also invented the matrix record, from which unlimited duplicate recordings could be pressed. Early turntables were operated by a spring-driven motor that required rewinding for each record played; later the use of an electric motor made rewinding unnecessary.

The quality of reproduction was greatly improved by high-fidelity amplification (popularly called hi-fi) and by complex speaker systems. From 1948 records were made to be played at slower speeds, thus lengthening the amount of material that could be recorded on a single disk; such long-playing discs were known as LPs. Stereophonic reproduction was achieved by adapting the phonograph to reproduce two channels of sound (see stereophonic sound). The first commercially available stereo recordings were produced in 1957. In addition to musical performances, records were often used to reproduce sound effects for radio and the theater, transcriptions of radio broadcasts, "talking books" for the blind, and lessons for language study. Most recording companies stopped producing phonograph records by the early 1990s in favor of cassette tapes and compact discs.

or record player

Instrument for reproducing sounds. A phonograph record stores a copy of sound waves as a series of undulations in a wavy groove inscribed on its rotating surface by the recording stylus. When the record is played back, another stylus (needle) responds to the undulations, and its motions are then reconverted into sound. Its invention is generally credited to Thomas Alva Edison (1877). Stereophonic systems, with two separate channels of information in a single groove, became a commercial reality in 1958. All modern phonograph systems had certain components in common: a turntable that rotated the record; a stylus that tracked a groove in the record; a pickup that converted the mechanical movements of the stylus into electrical impulses; an amplifier that intensified these electrical impulses; and a loudspeaker that converted the amplified signals back into sound. Phonographs and records were the chief means of reproducing recorded sound at home until the 1980s, when they were largely replaced by recorded cassettes (see tape recorder) and compact discs.

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