1. A strong ultrasonic signal frightens animals. The animals avoid the area because of its unpleasant ultrasonic sound. The sound is activated when an animal enters the range. Thus, animals cannot get used to the sound, and the repulsive effect is stronger. 2. A strong flashing scared animals. The strong flashing is activated when an animal enters the range, then the animals will be scared and give back.. BUTTON "FREQ" POSITION 13.5kHz-17.5kHz Repels animals such as mice, small rodents ... 15.5kHz-19.5kHz Repels animals such as large dogs, foxes ... 19.5kHz-23.5kHz Repels animals such as small dogs, cat, bird, bat ... Strong flashin All functions working, sweep frequency from mode 1 -- mode 2 -- mode 3, and turn on strong flashing