I got one years ago for Fizbin in herding. He doesn't have a real reliable stop and I thought that would be an easy fix. I had not used an e-collar before and I didn't accomplish the results I wanted.
Now fast forward a few years. I have started taking private obedience lessons. I was using a tennis ball as a reward. We were in a HUGE private field. Fizbin went after the tennis ball and kept on going. He refused to come back so I had to hunt him down. It took awhile because it was a huge field and Fizbin then decided to play keep away. I didn't engage in the keep away game, and was able to grab him when he realized I wasn't where I was supposed to be.
So my instructor told me to find my e-collar and have Fizbin wear it nearly every day for the next two weeks. The collar is not on and we do our normal activities, including lots of fun stuff.
We have our normal lesson and after a few minutes of doing heeling work, I release him while my instructor and I chat. When he is about 15 feet away called him. He blew me off. Instructor zapped him on a rather low setting. He jerked and I used my happiest voice and he came trotting back.
Repeat normal training session and repeat the letting him wonder. The second time I called him, he started to turn, but he wasn't looking at me. So instructor zapped him again. Again, lots of happy voice, praise and reward when he got to me.
We finished up the lesson and she told me to just let him go on ahead of us. I called him when he was about 20 feet in front. He immediately turned and headed towards me. To increase his speed, I started moving backwards. When he passed my instructor, he gave her the evil eye.
The next day I went to a different place to work on obedience. I had him off lead in a fairly safe, but open place. I let him pee on two bushes, and then called him towards me. He decided he needed to pee some more, so I zapped him. He got the point. His heeling was spot on. His stays under distractions were perfect. He seemed happy and relaxed. I didn't need to use it during the rest of the training session.
Now for the small print. Fizbin's formal recall has gone down the tube. He will not come on the first call. He will no longer play ball, even tho no ball was present during the e-collar training. I know those things will come back with extra patience and practice. As all things, you fix one thing, but two things break.