PortableUltrasonic Insect Repeller Applicability Home, Apartments, outdoor.barbecues, camping, fishing, the beach, picnics or other outdoor activities etc. Principle:Dragonfly is the natural enemy of mosquito. This product can imitate the sound of dragonfly wing`s vibration to make them painful and discomfortable and then flee away.How to use:1.The device imitates the sound of dragonfly wing`s vibration to drive all kinds of mosquitoes.2.Press “I”, the sound will last for 2 minutes. Meanwhile, the red light will flash every one second. After 2 minutes, the red light will stop flashing.3.Press “II” for the first time, the sound will last for 2 hours and red light flashing every one second. Second press, it will last for 4 hours and Third press, 6 hours. After fourth press, it will stop working.4.Push the top switch on the left side and you can use it as a flash light.Technique Data: