This circuit was obtained from the February 1992 Radio Electronics magazine. In it, a bar of 4 LEDs flashes continuously at a speed given by C1 and the setting of R3.
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...