Perimeter collars are electric shock collars. They are cruel and inhumane, and also they just don’t work.
Many dogs get neurotic and depressed from the shocks and then end up freaking out and running past the perimeter. Many other dogs are crafty and figure out how to stand close enough to the line to activate the collar’s sensor but not the electrocution component, thus wearing down the battery. Then they dip out.
–RSPCA is against electronic containment fences https://www.bbc.com/news/uk-england-45320038