The ornamental design for a signalconverter, as shown and described.
FIG. 1 is a front, top and right side perspective view of a signal converter showing our new design;
FIG. 2 is a rear, bottom and left side perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a left side view thereof; and,
FIG. 8 is a right side view thereof.
The signal converter is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.