The robot mower system starts with a base station which has a direct connection to mains electricity. This base station creates a signal which goes out along the perimeter wires which are attached to it. The base station creates other signals which go out along the guide wires, it also emits radio waves in different frequencies and patterns which help the robot mower or automower guide itself back into the base station for re-charging it battery.
Some models of automower and robot mower have their own onboard GPS ( Global Positioning System ), and are capable of learning the shape of your garden as they mow the grass within the perimeter wire.
Some models of Automower or Robot Mower have Ultrasonic “vision” built in which helps prevebt the mower from bumping into obstacles ( eg Garden Ornaments ) which cutting the lawn.
Most models of Automower from Husqvarna have their outer housing mounted on magnetic pillars, so that when the automower bumps gently into an obstacle the alignment of the magnets is disturbed and this signals to the mower to gently reverse and go in a different direction.