The ultrasonic pest repeller designed by ultrasonic & electromagnetic technology. Due to electromagnetic properties of this unit,use Electromagnetic Ultrasonic Pest Repeller one unit per floor. The electromagnetic waves will work through walls. The unit repel ants, cockroaches, mosquitoes,mice and so on. Non Chemical, Non toxic, Non Noise. It is safety for humans and pets. Night Light - Help see your way through a dark hallway, kitchen bedroom bathroom or any where you want to plug pest control in.