The ornamental design for a wirelesstransmitter, as shown and described.
FIG. 1 is a perspective view of a wireless transmitter showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines showing portions of the wireless transmitter represent unclaimed portions of the claimed design and form no part of the claimed design.