How does the Friendly Robotics Robomow system work?
A wire is laid around the outer edges of the lawn. The wire is attached to the surface of the lawn with pegs every few feet. When connected to a small battery powered current source, called a Perimeter Switch, the wire forms a virtual fence for Robomow®, containing it to the area you are mowing. This is a similar type of technology that invisible pet containment systems use.