Disguised as a birdhouse, the Elite Outdoor Bark Control has an internal microphone that picks up the sound of your dog barking, then sends an ultrasonic tone to correct his behavior. The tone persists 3 seconds after your dog barks and then is silent again until it hears another bark. This weatherproof device is our premium outdoor barking deterrent because it comes with a built-in digital timer. The timer works like an alarm clock, turning the unit on and off at specific times to help your dog from becoming desensitized to the ultrasonic tone, and to conserve battery life. Our ultrasonic tone is a sweeping, wavelike sound that catches your dogs attention and is harder for him to ignore than other consistent tone deterrents. The sound is inaudible to most humans, but sends a clear signal to dogs. Dogs quickly learn to associate their barking with the sound, and most dogs curb excessive barking within 2 weeks. Your pet deserves the best. Trust PetSafe to help keep your pet healthy, safe and happy.