This is combined with special collars the dogs wear to warn them to not cross the fence boundary. (dogingtonpost.com)
Also, kittens need special collars, because their system can not handle the toxicity of an adult cat collar. (howtoguides365.com)
You can do this at home by making a sleeve or soft fabric through which you can insert the collar or you can look for special collars for dogs with sensitive skin that have a layer of special cushioning. (dogtrainingbasics.com)