Scare off the unwanted guests like Rats and Cats from your home. This Ultrasonic transducer emits inaudible ultrasound which makes a hostile environment for the pests like rats. Even though human beings cant hear ultrasound, most of the animals can hear the ultrasound. Some frequencies of the ultrasound create stress on the animals and they avoid its presences. Animals like Rats, Cats, Dogs etc responds to the ultrasound frequencies between 28 kHz and 60 kHz. The output frequency of this circuit can be varied from 20-60 kHz using a Pot. Remember, animals are more intelligent and adapted than us and sometimes they will be immunized to a particular frequency.