Provides simple buttons and UI. Support background execution! Background launch allows you to use other apps at the same time. principle: Female mosquitoes hate the sound of male mosquitoes. Provides two simple ultrasonic waves. # Silent - Home mode: 20kHz ultrasound is provided in an area that can not be heard by humans. # Outdoor mode: The frequency automatically changes from 10 kHz to 20 kHz to cope with various kinds of mosquitoes.