This Anti-Bark Collar stops barking by progressively increasing the sound and shock levels within the collar. This collar is controlled by a microprocessor, which distinguishes your dog's bark from other environmental noises and automatically delivers shock after each bark. This pattern is repeated through 7 correction levels. The first two levels present a progressive warning tone. If your dog continues to bark through the rest of the five levels, a more intense sound and shock will be applied after each bark for a 30 second duration until your pet stops. Once your dog has stopped barking, the Anti-Bark Collar will automatically reset to the first "tone only" level of correction. To protect your dog, if continuous stimulus reaches the 7 levels, the collar will automatically stop working for 1 min. The Anti-Bark Collar is semi-automatic. Just install a 6V alkaline battery, adjust the strap to the size of your dog's neck, and the collar begins the job. There are two BUTTONS used to adjust the sensitivity to the bark, and every time there will be "B" out of tone, sensitivity will gradually be enhanced or weakened. The more sensitive, the easier to trigger the collar.