Actually, it would be simpler to leave out the screen, pushrods and cams entirely.
Just have the face of the characters coloured so that they are visible against the belt, and viewed directly.
But it occurred to me that the length of the belt would be impractical.
52 letters, upper and lower case, 10 digits, space, math symbols and punctuation, plus the spacing between characters, the belt would probably be at least two meters long just to show characters a centimeter wide!
You'd always be replacing broken belts!
Nah, I'll just throw my vote in with the split flap display, a much better solution than mine!