Ultrasonic dog repeller, Zootovary, Kyiv

Compactultrasound deterrent dogs will help protect you from attacks by stray dogs
It has 3 modes of operation: a flashlight (will help illuminate the road, find the right key, etc.); training (sends an ultrasound signal, imperceptible to human hearing, but audible to a dog. In a certain combination, it can work as different commands, replacing, for example, a whistle); scaring (powerful ultrasound signal, unpleasant for the dog)(//tractor-service.com)
Power supply: 9 V crown (not included in the delivery set)
Dimensions: 130 x 26 x 40 mm
Subjective opinion: the device definitely works on dogs. Even at a great distance, dogs pay attention. "Unfamiliar" street dogs immediately run away. I almost had to poke my yard dog, which I see almost every day, with arepellent so that it would run away (apparently, it did not expect aggression from me :). There is also an opinion that it works worse on old dogs, but at the same time, old dogs are unlikely to show aggression.