In the event of an unexpected power cut, the robot lawn mower will stop immediately. Although the robot lawn mower itself is battery powered, the perimeter wire has a current running through it, which the robot lawn mower detects and is essential for its operation. Therefore, when power to this is interrupted for any reason, the robot lawnmower will stop until such times as power is restored. Once power is restored, the mower will revert to its previous activity, with no loss of settings.