Ultrasonic dog deterrents work by emitting a high-pitched squeal that is annoying to dogs, but inaudible to people. The most common devices are hand-held and work at the press of a button. These are generally for personal use when walking or jogging. With the use of a bark-activated device, though, you can set up a system that will keep dogs out of your yard -- or train them to stay in certain parts of the yard.
Determine which parts of your yard you want to keep dogs out of. Then find places where you can mount the dog deterrents. Ideally, you should mount them no more than five feet above the ground. You can use adhesive strips to attach the deterrents to your house, or you can wire them up to a fence or to a tree trunk. If you are trying to keep your own dogs in one part of the yard, use the natural barriers of the house or garage to block the sound. A device attached to the front of the house will send the sound to the front yard, but will not annoy dogs in the back yard.
Set the range on the device. The most common bark-activated deterrents have range settings of 15, 30 and 50 feet. Use as many devices as you need to cover the entire area you want to keep free of dogs.
Check batteries and mountings at least once a month. Batteries will usually keep a deterrent activated for at least two months. Mountings are affected by weather conditions and should be checked to make sure they remain secure.
The sound in an ultrasonic device does not travel well through solid or semi-solid barriers such as walls or hedges. Keep this in mind when planning where to mount your devices. Remember that the device is triggered by the sound of a dog's bark. It can be useful to train your dogs to stay in the back yard, but it does not differentiate between particular dogs, so it cannot be used to train some, but not others.
If you have dogs of your own, these devices will repel those dogs as well as strays from the areas where you set them.