Describe Working Principle - Ultrasonic pest repeller with the latest technology of automatic frequency conversion, produce different ultrasonic bands and change continuously different frequencies, can stimulates and interferes with the auditory and nervous system of mouse. Making pests like mice, flies, mites, bed bugs, etc. feel uneasy and uncomfortable, and force them to leave your premises. 3 in 1 Repelling Effect - repellent with triple ultrasonic frequency range - ultrasound, sawtooth wave & bionic wave, increases its strength to expel all indoor pests of 800-1800 ft. And the wave is 360 degree all around coverage, let mice and other pests have nowhere to hide. Easy to install and work - Place our ultrasonic repellent 31.5-47.5 inches from the ground, simply plug in our electronic pest control and it will do the rest when lighting 3 colored lights. Usually you can see the effect within 3-4 weeks, depending on the degree of infestation.Make sure that the repeller is not obstructed by furniture or electrical appliances when in use. Absolute Safety for Humans and Pets - Ultrasonic Pest Repellent is safe, non-toxic and radiation-free to human body. There will be no need to worry about your kids, baby, dogs, cats, fish, rabbits are being harmed. With advanced ultrasonic control you can eliminate pests with humane treatment but harmless to children or animals. And you don't have to kill mosquitoes with chemicals and clean up their remains afterwards. Package included : 2 X Ultrasonic Pest Repellers