Hiado Dog Anti Barking Training Collars Devices for Dogs with Vibration Only How it works? the device vibrate when your dog barks. The vibration is enough to attract dog's attention and dog stops barking Please adjust collar to right size, make device probe to touch dog skin, otherwise dog can not feel the vibration Safe and humanity: no electronic shock hurt to your dog It works better for small dogs. Suggest working indoor Both sound and vibration sensor sensitivity are adjustable. (find product picture here for reference)