phonograph

Cutaway of a phonograph (record deck) with belt drive and anti-skate pickup arm

Also called a record player, an instrument for reproducing sound recorded mechanically as modulations in a spiral groove. It was invented by Thomas Edison (1877), whose first machine had a revolving grooved cylinder covered with tinfoil. Sounds waves caused a diaphragm to vibrate and a stylus on the diaphragm made indentations in the foil. These could then be made to vibrate another stylus attached to a reproducing diaphragm. Wax disks and cylinders soon replaced tinfoil, then, when by etching or electroplating metal master disks could be made, copies were mass-produced in rubber, wax, or plastic.

The main parts of a record player are the turntable to rotate the disk at constant angular velocity; the stylus, which tracks the groove and vibrates with its modulations; the pickup or transducer that converts these piezoelectrically (see piezo-electric effect) or electromagnetically into electric signals; the amplifier and the loudspeaker.

Related category

• ACOUSTICS AND MUSIC
• TECHNOLOGY

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Encyclopedia of Alternative Energy & Sustainable Living
Encyclopedia of History

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