We purchased Dog Guard about 5 years ago for our puppy Jack Russell. What a godsend!! We put it in when our puppy was 5 months old. She responded immediately and training was a snap! It took no time at all to have her protected. Even in the dead of winter, she'll run all around the border in glee when the snow plows come by or any other truck of her fancy. She has never broken through the line and respects the system completely. We even put it up at our camp which is on a busy road; again, she runs the line, but never breaks through. Some dogs, especially those like Jack Russells, should never be without Dog Guard protection. Dogs need to run and have safe boundaries. We never worry about her and she leads a healthy life thanks to all the exercise she gets. Without Dog Guard, too many dogs are confined to small yards or worse. With this system, dogs and run around and around their master's home releasing energy and having plain ol' fun. We are very grateful to Dog Guard for their devoted training and Dog Guard system. We have one very happy dog thanks to this company! Lauren & Kevin Carpenter