The integrated circuit used in this circuit from a 1987 documentation is no longer common today. This circuit can generate a multitude of different sounds and this circuit is an example of application.
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...