Dogs weren’t always waiting by the door for snack time. Long ago, their hearing played a crucial role in survival. Dogs are designed to hear significantly higher frequencies, up to 44,000 Hz, than ...

It’s well known that many animals are particularly sensitive to high-frequency sounds that humans can’t hear. Many commercial pest repellers based on this principle are available, most of them ...

This ultrasonic dog repeller circuit will chase away angry dogs. It is build with the all known 555 circuit, a buzzer and a little ferrite transformator. The ultrasonic frequency must be set with a ...