This is the work of Dave Kellogg. I'm just passing it along.
Many drill presses and mill/drills use three pulleys and two belts. A variety of spindle RPMs can be achieved. It isn't all that hard to adjust, but it is a distraction. When I'm focused on the task at hand, I'd rather not have to stop and think about shifting belts. The sign offered here minimizes this annoyance. Dave's spreadsheet is also offered. You can change the RPM values and generate a sign that fits your needs.
If you are interested, please see
Your comments are welcome. All of us are smarter than any one of us.