This circuit was originally intended for reading movie soundtracks. The circuit is from 1967 and was found in an English publication. The sensor is semiconductor type.
This circuit is from a 1968 publication. Here we have several types of resistive sensors with...
This circuit was obtained from an English magazine from 1976. The transformer has a current of 1.5...
This step is also suitable for the AC188k and SK3004 transistors and was found in a 1980s...