... is effective in the 160 squaremeters room.Characteristics:1.The Frequency inverter ultrasound(20k~55kHZ) is no smell,no harm,and no ... (220V).2.Put Ultrasonic choosing switch on Varible gear.Output Frequency-Inverter Ultrasound.red Led works in the middle off gear,no ... ultrasound output.3.If puting on Fix gear.Output Steady-Inverter ultrasound.Green Led works. electronic ultrasonic mosquito repellent