This circuit was obtained from an American documentation from the 90's. The components can be changed, and a power step can be added for greater sound volume.
This circuit was found in an old publication from 1989 but can still be assembled today with BD135...
We found this circuit in a 1987 documentation. Its purpose is to turn on a garage light using the...
In the figure we have a simple logic level indicator for TTL circuits or powered by 5 V....