If there's something more annoying than constant barking, it's an ultrasonic tone; good thing humans can't hear it! with the PetSafe Ultrasonic Indoor Bark Control, there's no need for bulky battery collars or static correction - set the unit on a table, turn it on, and that's it! Every time Buster barks, the UltraSonic Indoor Bark Control emits a high-pitched, ultrasonic tone only your dog can hear. Buster's gonna learn - no barking, no annoying squeal. Win-win!