I have 2 dogs %26 another that visits a lot, 1 barks a LOT so I thought I'd try this out because I wasn't going to use a shock collar and WOW, they really respond to it! The silent ultrasonic button gets their attention right away! We're working on associating it with barking but yes, it's great at stopping them in their tracks humanely. Also for what it's worth, you can use this to call them from another room or to come inside.
Instructions came with it along with a website for a video with more in depth information.