Using the latest ultrasonic technology, the SUPER DOGCHASER is one of the only electronic animal repellants that uses two ways to repel a dog. One is the discomforting but not harmful high frequency sound (20,000Hz-25,000Hz), audible to dogs but not to humans. And, the second is a super bright LED flashing strobe that temporarily blinds and confuses the dog. We think this is the best dog repellent because it won't harm the animal. Helps stop the approach of unwanted dogs up to 40 feet. Also has a training setting. Requires one 9 volt battery. These electric dog repellents can also be used as a flashlight.