A Record Word-Spotting Mechanism

The record word-spotting mechanism described here places the pick-up needle upon a predetermined spot on a phonograph record by pressing a remotely located release button after three reference readings, previously established by the trial and error method, have been properly set. The pick-up arm is held poised above the record by a direct electromagnetic pull upon the back end of the pick-up arm. When the electromagnet is de-energized, the pick-up falls due to the pull of gravity. The speed of fall may be controlled by means of an adjustable exhaust port on an air dashpot. No catches or latches are used in releasing the arm. A manually operated open-circuiting release button is in parallel with a second open-circuiting switch in the electromagnet circuit, the second switch being opened each revolution of the turntable by a cam. To release the pick-up, the manually operated button is depressed, but the pick-up is not released until the second switch is cammed open by the turntable. In this way the device is indexed with relation to the radial position of the record so that not only may the correct groove be repeatedly selected, but the desired portion of the groove may be consistently repeated. The effect of eccentricity of the center hole of the record with relation to the recorded grooves is also eliminated. Variations in the size of the record hole are accommodated by means of a tapered centering pin. Each of the mechanical parts, with the exception of the cammed turntable switch, is rigidly located on the single pick-up arm unit. All necessary electrical parts for complete operation of the mechanism on 105- to 125-volt, 50- to 60-cycle alternating current are located on the under side of the motor board.

Print ISSN

0097-5834

Published

1937-01

Content type

Original Research

DOI

10.5594/J08593