There was one dog [huge bearlike beast with agressive disposition] I used to encounter on my early morning walk. They had the buried wire installed and he had the zapper collar.He would snap and snarl near the flags even though I would always go to the far side of the street. One day the bear thought it better to endure the pain than to let me pass one more time.He came on thru with a yelp and that just made him all the nastier.He came in low and fast ,snapping and blowing spit all over me.Thank heaven I had the walking cane with me,it still has the rasping teeth marks in it. I now will never trust a buried wire or a nasty dog to do the right thing. I am so glad they moved because after that experience, if he ever came for me again that would be his last.