This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit uses a unusual optocoupler that can be replaced with an equivalent one.
This circuit was obtained in a Hobbyst Handbook from 1990. The circuit can be easily assembled...
This circuit was obtained in an old American documentation. The integrated circuit used is...
This circuit produces a signal that has the waveform of the sound produced by or near the banjo....