Patent ID: 7613543

Claim:
Method for operating an automatic device ( 2 ) by means of an electronic directing system, said system comprising at least one first electrical cable ( 1 , 4 , 5 , 6 ) connected to at least one first signal generator ( 3 , 7 , 8 ) and at least one sensing system ( 11 , 12 , 13 ) arranged on said device ( 2 ), said sensing system ( 11 , 12 , 13 ) detecting at least one magnetic field being transmitted via said cable ( 1 , 4 , 5 , 6 ) and propagating through the air, the sensing system transmitting a processed signal to at least one driving means which contributes to the movements of said device in relation to a surface, characterized in that said first signal generator ( 3 , 7 , 8 ) transmits a current through said first cable ( 1 , 4 , 5 , 6 ), said current during a part of time is in a state of rest were it is substantially constant, said state of rest periodically being interrupted by at least one first characteristic current pulse ( 20 ) and that said sensing system ( 11 , 12 , 13 ) synchronizes the time intervals ( 28 , 29 ) within which the system ( 11 , 12 , 13 ) detects magnetic fields based on the properties of said first current pulse ( 20 ), said first current pulse being transmitted through an electrical cable ( 1 ) that substantially demarcates the area within which the automatic device ( 2 ) intends to operate.