This circuit has a normally low output that is triggered by a high pulse. The circuit is from Radio Electronics from November 1984. The frequency is given by C1.
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...