This electronic dog repellent product has a  high frequency sound (20,000Hz-25,000Hz), audible only to dogs but not to humans. It also comes with a  bright LED flashing strobe that temporarily blinds and confuses the dog. This dog repellent helps stop the approach of unwanted dogs up to 40 feet. It Also features a training setting. Requires on 9 volt battery. You can opt to use it as a flashlight as well.