This circuit was found in a 1968 documentation. It makes use of both NO and NC reed-switches and small magnets attached to a card in the form that results in the drive combination.
Published in Popular Electronics with the curious name of Obnoxious Noisemaker, this 1968 circuit...
This preamplifier circuit for turntable cartridges was found in the March 1994 issue of...
E) This circuit was found in documentation from the 1980s. The integrated circuit used is not very...