Petsafe Indoor Bark Control 2 Pack The Petsafe Indoor Bark Control 2 Pack uses ultrasonic technology to help reduce unwanted barking inside your home. When your dog barks, the device emits a high-pitched tone that is audible to dogs but inaudible to humans. Over time, your dog learns that barking triggers the sound, encouraging quieter behaviour. Compact and discreet, each unit stands just 3 inches tall and can be placed on a table or mounted on a wall or door frame using the included adhesive-backed hooks. This pack includes two devices for larger homes or multiple rooms. Benefits and features Ultrasonic technology to discourage indoor barking High-pitched tone audible to dogs but silent to humans Compact, discreet design fits on tables or walls Includes adhesive-backed hooks for easy mounting Two devices included for larger areas or multi-room coverage Easy to use, plug-and-play setup