[linz06]

I know the ultrasonic things work, at least one time that i used it. My dad has one for work because he has to go into peoples yards to read their power usage and work on power lines on farms and stuff where there are a lot of dogs around. He brought it home one day and I tried it on my brother's miniature american eskimo puppy and as soon as i pressed the button he shut up and his ears perked up. They also have ones that you can just put in a room and it'll detect your dog's bark so you don't have to be around and you also don't have to put a collar on your yorkie which is a hazard. Hope this helped!