There is a switch on the side of your transmitter, it may read "A,B,C" or "High, Low". The settings on the A, B, C switch help to adjust the resistance in your containment perimeter. Use this feature, along with the range dial to adjust the distance from the wire to the point where your pet's receiver collar will activate. Many factors will determine which setting is the best for you (the amount of wire in your layout, interference in your yard and home, your wire layout, etc.). Please try all 3 settings individually to determine which is the best option for your perimeter.