Photoshop :: Adjusting A Grayscale Scan

a grayscale scan of a line drawing with small text. The lines and text, which should be black, are gray. And the background, which should be white, is a light gray.

The lines should be 100% black, but I'll take what I can get. I fiddled with curves and contrast and stuff, but when I'd get the background adjusted so it was completely white, then the lines weren't dark enough.

And of course converting to a bi-level bitmap made the lines and text all pixelly

this will be offset printed, so it needs to be high resolution.