How to test the bark collar before wearing on your dog: 1.Dial gear to P to turn on the bark collar - You will see a green led light flash slowly. 2.Blow toward the sensor (between 2 inside prongs) – You will feel seconds vibration and red led light flashes 1 time. It works. How to properly fit the bark collar on your dog: The inside prongs must be against your dog's neck skin (1 or 2 fingers gap) to work. How to operate the 3 modes of the bark collar: 1.No Shock Mode - Vibration Only Dial gear to “P”. That’s it. The bark collar will vibrate your dog to get his/her attention when barks. 2.Automatic Mode Dial the gear to “A”. It will starts at the lowest level (2) and progress to the next (max 5) and return to the lowest (2) when dog does not bark within 30 sec. 3.Shock Mode – User selected correction mode Dial the gear to “2, 3, 4, 5”. When your dog barks, collar will be vibrate first, then shock at the level you set. How to check the bark collar works or not: ✔The green led light flashes slowly when the bark collar on. ✔The red led light flashes rapidly for 5 times with vibration or safe shock when the bark collar detects the bark from you dog. ✔The red led light flashes rapidly for 10 times when the battery is low. ✔No light when the bark collar off.