As well as a pet training tool it can also prevent dog attacks. Suitable for outdoor / indoor work, travel and security. Ultrasound design - based on the theory that ultrasound effectively trains your dogs to be obedient and stop unwanted behaviors such as barking, digging, chewing and more. 100% Safe to humans & Harmless to dogs. This device emits ultrasound that can not be heard by the human ear. Uses one 9 Volt battery (not included). Perfect to take along while walking, jogging , cycling, etc. Dimensions are 5.1x1.6x0.8 inches. Fits comfortably in your pocket.