... not only can drive housefly away ,but also have good function of repelling cockroaches, mosquitoes, ants, fleas, spiders, centipede, 4.This ... to Use:Ultrasonic housefly repeller insert into the 220V power outlet, the green light shows that power supply is working. ... red light will blink, flicker frequency with the same frequency of the ultrasonic wave. Ultrasonic housefly repeller should be continue ...