I was mowing a yard and 2 big dogs were outside next door. There wasn't a fence and they were not chained up either. I had to just get done though so I tried to ignore them. They were barking and wanted me for lunch though. When I got close to there yard with the chopper they charged at me in attack mode, but then all of a a sudden they started getting shocked and freaking out. They ran back to there yard. After I was finished the owner came out and said don't worry they have shock collars on, and if they go outside the invisible fence that is buried they will get shocked. It was pretty funny to see these dumb dogs getting shocked.