We found this circuit in the Radio Electronics Handbook magazine special edition of 1992. The circuit uses an optocoupler as an electronic potentiometer.
In the figure we have the adapter circuit for connecting a headphone to the output of a stereo...
Found in the June 1972 issue of Radio Electronics magazine, this circuit generates signals that...
The output of this circuit must be connected to the input of an audio amplifier. The microphone is a small...