The PBC-102 Collar starts with the lowest level of static correction and then increases through 6 levels each time your dog barks within 30 seconds of the previous bark. If your dog does not bark again within 30 seconds, the collar will reset itself to the lowest level of static correction. Along with each static correction there will be an audible beep. The PBC00-10677 Collar has the same features as the PBC-102 Collar, as well as, a unique patented sensor technique that provides the most reliable bark detection available. It used both vibration and sound sensors to discriminate each bark from other external noises. Both collars have the built in safety feature that if your dog barks 15 times or more within a 50-second period, the collars will automatically shut off for 3 minutes. Non-returnable 3 days after receipt.