Koolatron PestContro Ultrasonic 600 Plug-In Pest Control Device - 3-Pack Each Unit covers a single room (approximately 600 sq. ft. of area) with ultrasonic protection Package of 3 offers multiple room protection Plug it in and the product begins emitting ultrasonic protection immediately Automatic Night Light built in to each unit A leader in Electronic Pest Control technology, our products have received recognition for design and function throughout the world. All of our products meet extremely high quality standards that are unmatched throughout the industry. "Lentek" brand Ultrasonic devices use ultra-high frequency sound waves that are set within the hearing range of rodents and other common household pests. Inaudible to humans, cats, dogs and most other household pets, the Ultrasonic frequency sounds like a