This circuit was found in a documentation for radio amateurs from the year 70. Its purpose is to produce a tone on a transducer when transmitting messages in SSB telegraphy.
I found this circuit in a 1992 Electronics Experimenter Handbook. The circuit can be easily...
Found in the February 1990 Radio Electronics issue, this sophisticated 100 MHz probe uses a period...
Found in 90s Popular Electronics, this circuit fires a load through a MOSFET from an audio signal...