PAC 500 Dog Training System - 500 Metres Range enables the handler simply and accurately to   address his dog with an appropriate correction, according to his misdemeanour. Without the dog realising that the correction is coming from his collar. The dog needs to think that the tone or level of correction with his trainer’s voice command or whistle is warning him of something “out there” which he needs to avoid, the correction is startling enough to get his attention and make him return to the handler for praise and attention.