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 an April 2000 Poptronics. The magazine no longer exists, but the circuit can...
We found this circuit in the Radio Electronics Handbook magazine special edition of 1992. The...
The integrated circuit used in this project is uncommon today, but the configuration can be...