The improvements bring improved low frequency waves that are safer for humans and pets and won't disturb your night's sleep. It includes sound generators that mimic predators by repelling foxes and raccoons with bionic waves. For heavily infested areas, use 5 units of repellent for effective pest and pest control. This is an advantage flea treatment for cats and dogs. Wide and Effective Coverage: Insect and rodent repellent is effective in indoor areas up to 1600 square feet. Widely used in homes, warehouses, offices, gardens, hotels, etc. We recommend that you install one of each, as ultrasonic waves cannot penetrate walls and solid objects. But for areas with severe infestation, we recommend installing 2 or more units in other rooms. If you install devices in one room, they won't work in other rooms. Safety and Environmental Protection: Ultrasonic insect repellent is chemical-free, non-toxic, low power consumption, silent to humans and pets, 100% safe, no need to clean up dead pests, no need to call pest control technicians for help, no batteries, save a lot of money . Easy to use: Just plug this wormer into the socket and perpendicular to the floor. Then the machine starts working when the blue light is on. For heavily infested areas, 2 or more pest control ultrasonic repellents are required. It usually takes 3-4 weeks to take effect. Note: White, UK version