The PetSafe® Deluxe Outdoor Bark Control includes a digital timer that can be programmed to turn the unit on and off at specific times, just like an alarm clock. When the Deluxe Outdoor Bark Control is within range of barking, an internal microphone picks up the sound and the unit is activated. The Deluxe Outdoor Bark Control emits an ultrasonic sound, which cannot be heard by most humans, similar to a dog whistle. Startled by the high-pitched sound, the dog should stop barking, as it will associate its bark with this unpleasant noise. The attractively designed unit will look right at home anywhere in your yard, whether it is hanging up or free-standing on a table or other area.