FIG. 1 is a front view of the radio transmitter unit embodying the design;
FIG. 2 is a rear view thereof;
FIG. 3 is a right-side view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a front and left-side perspective view thereof.
The broken lines in FIGS. 1 to 7 show elements which may be part of the environment of the design and form no part of the design as claimed.