Method for configuring an interface of a welding power source (31, 41, 51, 61, 71, 81, 91), the interface comprising at least one external terminal (201... 206), characterised in that - the interface (32, 42, 52, 62, 71, 82, 92) is represented as a graphical interface symbol of the at least one internal terminal (101... 105) thereof and the at least one external terminal (201... 206) thereof, - interface functions are represented as graphical interface function symbols (301... 321), an interface function symbol (301... 321) being arrangeable between the at least one internal terminal (101... 105) and the at least one external terminal (201... 206) of the interface symbol so as functionally to link the at least one internal terminal (101... 105) to the at least one external terminal (201... 206) via the associated interface function, - a) the external shape of the interface function symbols (301... 319) and of the interface symbol is configured in such a way that the interface function symbols (301... 319) and the interface symbol fit together in the manner of puzzle pieces and/or in terms of colour if the associated interface functions match the at least one internal terminal (101... 105) and/or the at least one external terminal (201... 206) in terms of function, and/or b) the outer shape of the interface function symbols (301... 319) is configured in such a way that the interface function symbols (301... 319) fit together in the manner of puzzle pieces and/or in terms of colour if the associated interface functions match in terms of function, and - said interface symbol and said interface function symbols (301... 321) are used for interface configuration, wherein a parameter of the welding device is assigned to an internal and/or external terminal (101... 105) and wherein logical linking of the interface functions is provided by stringing together the interface function symbols (301... 321). - the interface (32, 42, 52, 62, 71, 82, 92) is represented as a graphical interface symbol of the at least one internal terminal (101... 105) thereof and the at least one external terminal (201... 206) thereof, - interface functions are represented as graphical interface function symbols (301... 321), an interface function symbol (301... 321) being arrangeable between the at least one internal terminal (101... 105) and the at least one external terminal (201... 206) of the interface symbol so as functionally to link the at least one internal terminal (101... 105) to the at least one external terminal (201... 206) via the associated interface function, - a) the external shape of the interface function symbols (301... 319) and of the interface symbol is configured in such a way that the interface function symbols (301... 319) and the interface symbol fit together in the manner of puzzle pieces and/or in terms of colour if the associated interface functions match the at least one internal terminal (101... 105) and/or the at least one external terminal (201... 206) in terms of function, and/or b) the outer shape of the interface function symbols (301... 319) is configured in such a way that the interface function symbols (301... 319) fit together in the manner of puzzle pieces and/or in terms of colour if the associated interface functions match in terms of function, and - said interface symbol and said interface function symbols (301... 321) are used for interface configuration, wherein a parameter of the welding device is assigned to an internal and/or external terminal (101... 105) and wherein logical linking of the interface functions is provided by stringing together the interface function symbols (301... 321).