This hidden W-227b is among the most reliable and economical pet containment systems available today. A buried wire transmits a harmless radio signal. When your dog approaches the boundary, the signal first causes the dog’s collar receiver to emit a warning beep. If your dog continues closer to the boundary, the system will issue a mild shock. If your dog continues further, the system will deliver stronger shocks until your dog is back within the boundary you have set. Your dog will naturally seek to avoid the correction and will simply stay within the set boundaries. field width control Audible and visual wire break indicators Anti-passing speed detection Built-in lightning protection Multiple collar operation Up to 5000 square meters of range (over 1.2 acres) Product Features: Levels The Receiver Collar features 7 easy to understand and adjust training levels plus an audible-only feature to ensure safe and proper training and containment for your pet. User Programmable Receivers