Work by ultrasound waves which can irritate with the brain and auditory nervous systems to powerfully drive most types of pest. No need to clean up dead pests, no bad smell and Corpses, no battery required and save a lot of money.Just plug the electronic pest control ultrasonic repellent in power sockets; It will start to repel the pests when the blue light on. It is effective up to an area of 1600 SQ; Put one in each room as ultrasound can not penetrate through walls and solid objects.The ultrasonic pest repeller working with low-frequency ultrasound waves, no noise in the room can influence you and your pets.