ALEKO UDR01 Ultrasonic Dog Repeller Aggressive Pet Repellant Deterrent Anti Bark Training Control Trainer Device Emits a piercing ultrasonic tone which is totally silent to humans but uncomfortable to dogs and other animals The tone is harmless to humans and animals, but any dog that hears it will want to get away from it as soon as possible Can be used to stay safe from strange animals when youre out walking, jogging, or cycling Also makes a great trainer for pets: a quick press of the button when training and your dog will learn to avoid the activity that triggers the tone Comes with convenient wrist strap for easy carrying; requires a 9V battery, sold separately