I have always hated invisible fences. I feel they are cruel towards dogs, why can't the owner watch them or give them a real fence? That way they wouldn't have to get that nasty shock. Besides if you go onto a property and there is no fence you may not know of a dog there. Yes they hide, unless you see " dog mines " you may not know the dog is there until BITE BITE CHEW CHEW. Well today I liked that fence!!!!! As the chow mix was just about on my leg "from nowhere" got his unexpected shock. Oh he yelped the people were not home but I am sure the dog didn't wander off the porch for awhile.