Deluxe Bark Control Collar18 total levels of correction. Progressive correction feature increases correction to next strongest level (in current setting only) if dog continues to bark. Safety time out will shut off the correction for 3 minutes if the dog barks more than 15 times in 50 seconds. Uses vibration sensor and microphone to sense for barking. 3 settings, High, Medium, and Low with 6 levels of correction per setting. Not recommended to use for more than 8 hours at a