The SPP6117A part (“Adaptor for Perimeter Wire”) is required if the resistance of the Perimeter Wire is bigger than 15 Ohm. Normally this happens when the Perimeter Wire’s lengths exceed 650 meters. In such case, a mower may start behaving strangely - running in circles or changing direction in the middle of the lawn. If this happens simply connect the adapter between the Base Station Head and the Perimeter Wire plot connector. Confirm that the mower starts working properly.