Richard,

Regarding scrolling display of text versus flash-card affects...

The reason the latter is not used is that there is no clocking keys for the viewer to know if he'll miss critical words if he looks away.

For example, if a display message was DO NOT OPEN THIS DOOR and each word was paused momentarily in the display, the reader may look away or sneeze during critical words and have no clue that they missed it. Missing NOT or other partials could invalidate the message value.

Scrolling has a big advantage. As you view and read the scrolling letters you immediately pick up the scrolling rate and thus KNOW what the word rate is, and whether you have time to look away etc.

I agree that scrolling is annoying in ways. Flash-card displays just are not the improvement.

aka j