This circuit generates sinusoidal signals between 300 and 3000 Hz. We find a 303 Circuits from the 90's. The operational ones are types with FET. The power supply must be symmetrical.
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...