Step 1 The pest repellent ultrasonic plug in emits low noise that only mice and pests can hear, keeping mice and flying insects away from your house. Step 2 This mosquito repellent indoor only needs to be plugged into the socket to start working. Simple operation and easy use. Step 3 The device stimulates and destroys the brain and auditory system of mice, making them panic and flee your house.Please be patient for 2-4 weeks, and the effect will become more and more obvious with time.