The invention relates to a method for operating a self-propelled lawnmower, which is moved on a surface (20). The surface (20) is surrounded by a border delimitation wire (21) on which electrical signals (16, 116) are transmitted. The transmitted signal (16) is received by at least one receiving coil (17, 18) in the lawnmower (2) and induces a reception signal (EI), which is evaluated in an evaluation unit (19). The evaluation unit (19) emits an output signal to a control unit (13), on the basis of which the control unit (13) controls the direction of travel of the lawnmower (2). In order to guarantee a safe operation of the lawnmower even in range of electromagnetic interference fields, the invention provides that the electrical signal (16, 116) is transmitted with a predetermined pattern (M). The evaluation unit (19) of the lawnmower (2) processes the reception signal (EI) as a pattern, wherein the pattern (M′) of the reception signal (EI) is compared to a predetermined reference pattern (RM). Information regarding the location of the lawnmower (2) inside or outside the border delimitation wire (21) is obtained from the comparison result. The control unit (13) will determine the direction of travel of the implement on the basis of this information.
