Before LEDs became cheap enough to be ubiquitous, flip-card displays were about the only way to get a digital clock ... attached to frames that hold a stepper motor and a Hall-effect sensor.

There is also a digital display in the center of the machine, which shows steps, elapsed time, calories burned, and reps per minute. The stepper is exceptionally quiet and is small enough to fit ...

We love them all, of course, but the great thing about [aeropic]’s display is how quiet it is — the stepper is mostly silent, and the segments make only a gentle clunk when they flip.