A:Answer The Motorola BARK200U shock-free no-bark collar offers instant feedback to your dog to discourage excessive barking. The collar senses the vibration produced by your dog's vocal chords when he barks and delivers a pulse of ultrasonic sound that is outside the range of human hearing. Unlike other deterrents, the collar can only be activated by the dog wearing it. The BARK200U also allows your pup 5 seconds of free barking to express themselves, making it a fair and consistent approach to limiting excessive barking.