Adjustable Frequency Technology & 2 In 1 – POIIOPY dog training device emits the high-pitched ultrasonic sound of different frequencies, which can avoid becoming immune to a certain frequency ultrasonic sound after a long time of adaptation and no longer respond to it, so you can use different sound waves alternately in each period of time. Use the Beep Mode before each use of ultrasound mode, so that some dogs can be conditioned to reflect, and they will react after hearing the Beep sound. Safe to You & Your Dogs – Unlike other electric shock dog training tools, POIIOPY ultrasonic anti-bark device uses the latest ultrasonic tech with Variable frequencies at 20HZ~20KHZ. The sound does not affect humans, but can easily grab the dog’s attention and stop their bad behaviors. Every time your dog makes mischief, simply Long press the button (the effective range is 16.4ft / 5m) and point the ultrasonic dog training device directly at the dog. Effective Dog Bark Control Device – POIIOPY ultrasonic bark control device provides a safe and effective solution to assist owners in controlling unwanted barking and stop some bad behaviors of dogs, such as excessive barking, digging, chasing, eat something dirty or fighting, etc. Works well on many sizes of dogs (except dogs under 6 months and aggressive dogs). Usb Rechargeable & Portable Size – Unlike other dog bark repellents using AAA battery, POIIOPY Ultrasonic Dog Bark Control Device with built-in 300mA Rechargeable Li-ion battery can last up to 20 days without worrying about no power. The small stop barking device fits perfectly in your hand. The Red LED light flashes when low power. Suitable for Indoor & Ootdoor Activity – POIIOPY dog bark deterrent can be used either indoor for stopping unwanted barking and house-training your puppies, and for those who are adventurers, the device can also be used for dog walking and training them to behave well in public and protect them from eating unsafe food.