Found in a 90s Popular Electronics, this circuit triggers a load from the audio signal applied to its input. The controlled load depends on the MOSFET.
Used with telephones at the time, this circuit was found in Popular Electronics from the 90s. The...
Found in a September 1992 Radio Electronics magazine article, this circuit generates a pulse as...
The circuit is from a 1966 English magazine, but it can be assembled with more modern transistors such as...