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.
This circuit is from Motorola's Linear Interface ICs from 1993. The MC1723 is the equivalent of...
T This circuit produces an audible signal when someone touches the sensor, or even approaches. The...
We found this circuit in a 1968 Electronics World. The transistors are from the era and...