This sophisticated repellent uses a double 555. We find it in an American documentation from the 80's. The circuit can be powered by batteries or source included in the diagram.
In the figure below we have the typical circuit of an automotive star alternator with the...
This simple pass-through circuit was obtained in an old documentation, but it is still up to date...
This circuit was obtained in a 1974 National Semiconductor components and circuits manual. The...