The DT Systems-190 Bark Collar features 9 levels of correction that deter barking in medium to extra large dogs (50lbs and up). The DT Systems Bark Collar picks up the vibrations from your dog’s vocal chords as it barks. The vibrations cause the DT Systems Bark Collar to send an electronic signal to your dog. Your dog when wearing a DT Systems Bark Collar will quickly learn that barking causes the signals, and that not barking is the way to avoid the signals. Uses one nine volt battery (not included) nine intensity levels selectable on a dial inside the battery compartment. Automatic 4 second delay between stimulations.