Found in American documentation from 1969, this circuit operates in the frequency range 10 to 150 Hz providing signals as shown in the diagram itself.
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...