We claim the ornamental design for a transmitter, as shown and described.
FIG. 1 is a front view of the transmitter;
FIG. 2 is a rear view thereof.
FIG. 3 is a side view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is a top, front, right isometric view thereof.
The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design.