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 traditional unijunction transistor configuration was found in a 1980s documentation. The functions are...
Found in a 1964 Electronic Design, this circuit uses transistors from that time. Equivalent...
Operating in the FM range, this is one of the many versions of FM transmitter that the reader can...