The Victor PestChaser Rodent Repeller emits ultrasonic frequencies that send mice & rats scurrying. It uses varying frequencies to prevent rodents from getting used to the noise & to keep them from returning. The high-frequency noise is loud to rodents & is safe for use around people & non-rodent pets when used as directed. It's also easy to use - just plug it into a wall outlet and let the device do the work for you. It includes an extra outlet at the base to preserve valuable plug space. Despite its small size, the Victor PestChaser Rodent Repeller offers mighty rodent protection. The plug-in repeller device is ideal for average-sized rooms including kitchens, bedrooms, attics, living rooms, & more. Ultrasonic frequencies can't travel through walls, so use one PestChaser per room you want to protect. The Victor PestChaser Rodent Repeller comes equipped with a built-in nightlight that emits a soft glow. The gentle illumination is not only great for navigating around obstacles at night but also lets you know the device is working. Note: Ultrasonic sound cannot penetrate furniture, cabinets, or walls. Multiple units required for multiple rooms. Rodents that are hungry or tempted by easily accessible food may find another route around your protected area, so it is best to remove all likely food sources prior to use. It works best to repel rodent populations when used with other rodent control methods as part of an integrated approach to trap, repel, and monitor infestations.