Variable Frequency Anti Bark Device for Dog,Ultrasonic Dog Bark Deterrent,2 in 1 Dog Bark Control Device，16.4 Ft Range LED Indicator,100% Safe Handhold Dog Training Tool Barking Behavior TrainerVariable Frequency Technology 2 Using Modes for choosing: standard frequency, Variable Frequency, WWVVPET dog training device can emit the high pitched ultrasonic sound of different frequencies, which can attract the dog's attention very well, avoid getting used to listening to the ultrasonic sound of constant standard frequency and no longer respond to it. EASY TO USE & EFFECTIVE When the dog barks or makes mischief, simply press and hold for 10s