Found in an Electronics World of 1969, this circuit causes a light bulb to flash along with the audio signal applied to the input. The circuit only works with incandescent lamps. C can be 47 nF to 220 nF.
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...