These products usually come as sprays or powders, and you can often find them at pet shops and garden supply stores. There are numerous scents manufacturers use to drive dogs away, and most products contain natural ingredients. Some of these dog repellants are meant to have a bitter smell that dogs dislike. Others actually smell like the urine of the predators and will thus scare dogs away. Motion-activated sprinklers are not only designed to water your lawn but also to scare off any visiting critters, including dogs, cats, and raccoons. Set these sprinklers up along the perimeter of your lawn or at any specific spot where visiting strays frequently do their business. As the dog passes in front of the sprinkler, the motion will set it the sensors, triggering a quick spray of water. This spray is enough to startle most dogs and send them scurrying away. Nothing keeps animals out quite like a physical barrier. Dogs looking for an easy spot to take care of their business will likely skip over lawns with fences in favor of those without. Make sure you keep the gate of your fence closed and periodically monitor the perimeter for holes dug by stubborn canines. If you already have a fence, check for holes that need to be repaired. It is also possible to purchase electrified fences, but that is an extreme solution. Ultrasonic repellents are also motion-activated. You can mount the mechanism onto a shed, tree, or fence. As the dog approaches, it will trigger the sensors, causing the repellent to emit sonic and ultrasonic sound waves that are intended to bother the dog. It is unclear how well these devices actually work. Until more evidence emerges supporting their efficacy, this should probably be your last resort.

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Write a summary of the previous text in Vietnamese:
Xịt thuốc đuổi chó. Lắp đặt vòi tưới nước cảm ứng. Dựng hàng rào. Sử dụng thiết bị đuổi chó bằng sóng siêu âm.