UPDATE TECHNOLOGY: The dual ultrasonic and electromagnetic chips of our ultrasonic pest repellers emit frequencies ultrasonic interfering the auditory and nerve system of the pest, making them feel uneasy and uncomfortable so that pests, mice, rodents and mosquitoes away from your home. Wide Effective Coverge : The Insect & Rodent Repellent is effective in an indoor area up to 1600 sq. ft. Its widely used in homes, warehouses, offices, gardens, hotels, etc. We recommend you to install one for each room because the ultrasound cannot penetrate walls and solid objects. But for areas with serious pests, we suggest install 2 or more devices for other room. They aren't effective for other rooms if you install device at one room. Safe & Environment Friendly: Ultrasonic Pest Repeller no chemicals, non-toxic, less power consumption, inaudible and safe to human and pets, no need to clean up dead pests, no more need to call pest control technician for help, no battery required and save a lot of money. Easy to Use: Just plug this Pest Repeller into the socket and vertical to the floor. Then the machine began to work when the blue light on. As for areas with serious pests, 2 or more additional pest control ultrasonic repel-lent is required. In general, it takes 3-4 weeks to make effect.