This setting simulates the sounds that rodents hear, proving that the product works normally under the condition of ultrasound.ULTRA = emit high impact variable ultrasound frequency at 22-35kHz.TRANS = emit solid ultrasound frequency at 25kHz. DUO = Both ultrasonic waves work at the same time -the repelling effect can be enhanced, and which can turn on automatically at night and turn off in the daytime, can repel target animals and decorate your place. The solar powered ultrasonic animal repeller repels animals by emitting ultrasonic waves and flashes of light. This device won't harm human and animal Effective in controlling rats, mice, roaches, fleas, crickets, ants and most of the other . It's widely used in homes, warehouses, offices, gardens, hotels, etc. This product starts to take effect within a few days after use. According to different use conditions, better effect can be seen only after continuous use for 2-4 weeks.