Sound track selector system for phonograph record players

In a sound track selector system for a phonograph record player, means for sensing respective bands of recorded and unrecorded sound, comprising a light emitting diode capable of emitting light primarily in the infrared region of the spectrum and a photo-transistor capable of detecting light in substantially all regions of the spectrum, including ambient light, said diode and phototransistor being mounted below the sound-stylus pickup arm and spaced apart in transverse alignment with respect to the axis of the pickup arm and such that the axes of emitted and reflected light are substantially parallel to each other and substantially perpendicular to the face of the record.

In a sound track selection system for a phonograph record, means for sensing the peripheral positions of the pickup arm comprising a rotatable shaft for the pickup arm, a disc mounted on said shaft below the turntable platform and rotatable with said shaft, said disc being provided with two slots radially spaced at different distances from the axis of rotation of the disc and one slot radially spaced from the axis of rotation of the disc at substantially the same distances represented by each of the aforesaid two slots, each said slot also being arcuately spaced from one another to represent positions of "rest," "return" and "play" with respect to the pickup arm, and an optical encoder assembly comprising a pair of light emitting diodes and a pair of photo-transistors in fixed position to register with the aforesaid slots and develop a corresponding signal when each said slot is rotated to permit light from a diode to be transmitted to the corresponding photo-transistor sensor, thereby producing a signal representing the position of the pickup arm.