Abstract: An optical acoustoelectric transducer receives light reflected by a vibrating board and detects the displacement of the vibrating board. A surface-emitting luminescent device having a substantially uniform concentric intensity distribution of light emission is placed in the center of a common substrate. A photodetector element is provided to surround the luminescent device. A lens is also provided in the optical path between the substrate and the vibrating board to converge the light traveling toward and from the vibrating board.

Abstract: An inclination detector is constructed such that a displacement detection plate of generally fan-shape is pivotally supported at its fan-pivot, a plurality of slits are formed in the displacement detection plate concentrically of the fan-pivot at predetermined intervals, and a light emitting element and a light sensitive element constituting a photocoupler are disposed on opposite sides of the displacement detection plate with the slits interposed therebetween, whereby when a slit is caused to move due to a vibration or slant and traverse the optical path of the photocoupler, a displacement of the slit due to the vibration or slant is outputted from the light sensitive element.

Abstract: A pair of positioning rings are engaged on the outer peripheral surface of a shaft, and a plurality of permanent magnets are provided on the outer surface of the shaft between the positioning rings. The permanent magnets are bonded to the shaft by a bonding agent which fills the spaces between the shaft and the permanent magnets, and an air gap is formed between the permanent magnets and the positioning rings, to allow thermal expansion.

Abstract: In a bearing system for a tone arm for use with a phonograph record player or the like where the bearing system includes a bracket for supporting the tone arm, a rotatable, tubular shaft connected to the bracket for permitting horizontal rotation of the tone arm, and a support for bearing the shaft including ball bearings or the like, the improvement of a suspension wire connected to the bracket at the upper end thereof and extending through the rotatable, tubular shaft; and a device for applying tension to the suspension wire to lessen undesirable movement of the shaft. The tension applying device preferably applies the tension to the suspension wire magnetically and may include a first magnetic structure connected to the lower end of the suspension wire and a second, fixedly positioned magnetic structure spaced from the first magnet structure where at least one of the first and second magnetic structures is a magnet.