This concealed W-227b is among the most reliable and economical pet restraint systems available today. A buried wire transmits a harmless radio signal. First, when your dog approaches the boundary, the signal causes the dog’s collar receiver to emit a warning tone. As your dog approaches the boundary, the system delivers a mild shock. As your dog continues, the system will deliver stronger shocks until your dog returns to the boundaries you set. Your dog will naturally try to avoid the correction and just stay within the boundaries you set. you have defined. Field width control Audible and visual broken wire indicator Passing speed detection Built-in lightning protection Multi-collar operation Range up to 5000 square meters (over 1.2 acres) Product Features: Levels The collar Receiver features 7 easy-to-understand and customizable training levels plus an audible-only feature to ensure safe, proper training and containment of your pet. User-programmable receivers have multiple settings