This hidden W-227B fencing system is the upgrading model of W227, which is rechargeable. It is among the most reliable, cost-efficient pet containment systems available today. A buried wire transmits a harmless radio signal. When your dog approaches the boundary, the signal causes the dog’s collar receiver to deliver a warning beep first. If your dog continues closer to the boundary, the system will issue a mild shock. If your dog continues further, the system will issue stronger shocks until your dog returns to within the boundary you have set up. Your dog will naturally seek to avoid correction and is content staying within established boundaries.