Cat and Dog Repeller
Nowadays, just about every house has an outside lamp with a motion sensor. Such a device eliminates the need to feel your way to the front door, and it apparently also scares away intruders. The only problem is that free-running dogs and cats in the neighborhood have little regard for such lamps and continue to deposit their excrement in the garden, once they have found a habitual location there for this purpose. This gave rise to the idea of connecting a sort of siren in parallel with the outside lamp to clearly advise dogs and cats that they are not welcome. Naturally, it would be nice to avoid startling the entire neighborhood with this alarm signal. Here we can take advantage of the fact that dogs and cats have a significantly better sense of hearing than people. Not only are their ears more sensitive, they can also perceive significantly higher frequencies. With people, the upper limit is around 18 kHz, but dogs and cats can hear frequencies in excess of 20 kHz. We can take advant...