This circuit produces the sound of percussion such as blocks, drum, bell, etc. The frequency depends on the marked capacitors, which can have a wide range of values depending on the desired sound.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...