Abstract: An electrostatic acoustic converter having two parallel, insulating perforated plates, the inner surfaces of which are covered by electrically resistive layers, each having a signal terminal for connection to a source of sound frequency signals. Between the plates there is fixed a flexible plastic diaphragm isolated from the layers and having a terminal for connection to a source of polarizing voltage.

Abstract: An electrostatic acoustic converter having two sound transparent electrodes between which a plastic membrane covered with a conductive layer is disposed. The membrane is fixed between two identical insulating plates having openings therethrough, in its greater part each of the insulating plates is coated with an electrically conductive layer which comes into contact with the conductive layer of the membrane and with a metal track with terminals. The metal track is fixed on an insulating card around a centrally situated metal plate having a terminal. The metal plate is multi-perforated and constitutes a sound transparent electrode.

Abstract: A mechanical compensator for the horizontal angular error of the playing arm of a record player. A lever is mounted upon and rotatable in a horizontal plane about a first bearing affixed to the base frame of the record player, the lever carrying a second bearing journalling a vertical shaft upon which the playing arm is mounted for joint rotation therewith. As the vertical shaft rotates during the second-tracking movement of the playing arm and the vertical shaft, a member affixed to the shaft is caused by a cam track to rotate the lever about the first bearing. The member affixed to the shaft may be a second lever having a cam follower which cooperates with a fixed cam, or the member affixed to the shaft may be a plate having a cam track therein which cooperates with a fixed cam follower.

Abstract: A compensator for the horizontal angular error of a record player arm. A first lever is disposed in a horizontal plane beneath the player arm, a first, fixedly positioned bearing supporting an intermediate portion of the first lever so that such lever can rotate in a horizontal plane. The first lever has a bearing on a first end thereof journalling a vertically rotatable shaft upon which the player arm is mounted for limited vertical motion with respect to the arm but so as to rotate horizontally with the vertical shaft. A second lever in the form of a flat horizontal optical mask is affixed to the vertical shaft to rotate therewith, the optical mask having an arch-shaped slit therein which is convex in the direction away from the axis of the vertical shaft. A source of light is disposed close to the optical mask on one side thereof, and two spaced photo-receivers are disposed on the other side of the optical mask.