The ornamental design for a signalconverter, as shown and described.
FIG. 1 is a front, top and left side perspective view of a signal converter showing our new design;
FIG. 2 is a rear, bottom and right 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 broken lines immediately adjacent to the claimed areas depict the bounds of the claimed design, while all other broken lines are directed to environment. The broken lines form no part of the claimed design.