What is claimed is the ornamental design for a signal device, as shown and described.
FIG. 1 is a perspective view of a signal device, showing the new design in a stop position;
FIG. 2 is a perspective view thereof, illustrated in a right-turn position;
FIG. 3 is a perspective view thereof, illustrated in a left-turn position;
FIG. 4 is a front elevational view thereof in a flat position;
FIG. 5 is a right-side elevational view of FIG. 4, the left-side elevational view being a mirror image thereof;
FIG. 6 is a rear elevational view of FIG. 4; and,
FIG. 7 is a top plan view of FIG. 4, the bottom plan view being a mirror image thereof.
The broken lines showing a person on a bicycle in FIGS. 1-3 are included for the purpose of illustrating the invention in use, and form no part of the claimed design.