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a component of the sound pickup that holds the pickup head and makes possible movement of the head from the edge of a phonograph record to its center.
A tone arm is usually a hollow metal rod. The pickup head is mounted on one end of the rod; the other end is equipped with a stalk that is used to rotate the tone arm in the vertical and horizontal planes and a counterweight that is used to adjust the pressure exerted by the pickup on the record groove. A special device ensures the smooth lowering of the pickup head onto the record.