This circuit with the 555, was obtained in a 90s American documentation. The signal must be applied to a good amplifier. The sound is similar to that of a police siren.
This circuit, from a publication from the 1970s, can be implemented with more modern transistors and 6 or...
This circuit switches off a load in case of excess current acting as a fuse. The circuit is from a...
This circuit was obtained from a manual of the integrated circuit itself, but can be applied to...