Protect your garden, plants or sandbox without chemicals or fences. When cats come within range of the motion sensor, the CatStop® automatic outdoor cat deterrent emits a sudden burst of ultrasonic sound (that humans can't hear) - the sound startles cats, and teaches them to stay away. Installation is easy - just place the CatStop in the garden or outdoor area that you want to protect, and it's ready to go. The built-in motion sensor detects the animal entering the area and emits a piercing, high decibel alarm. The startling and annoying noise frightens cats away. Since the sound is ultrasonic you and your neighbours should not hear it.