The dog repeller arrived in time. From the various reviews that I've read online, dog repellers may work in some cases and not others. In my case, we have 2 small dogs next door and bark every time we walk into the back yard. So this purchase was for the purpose of quieting them down so that we gain our peace back while in the back yard.I tried this product on the Maltese. When I triggered the ultrasound, she continues barking at me. Whether or not she hears the sound is not relevant as this product did not change her behavior.I think I will continue my quest for a good alternative.