A brass disk spins very fast. As it slows down the shortest "tooth" vibrates. As it further slows the longer teeth vibrate one at a time. A resonance, or vibrating-reed, tachometer uses a series of consecutively tuned reeds to determine engine speed by indicating the vibration frequency of the machine.

A heavy and light mass of equal length swing with the same period.

The UCM of a rotating disk is compared to the SHM of an oscillating spring. The comparison is shadow projected.

Driven mass on spring & power supply. A motor provides the forcing function that drives a torsion wheel. The labels are in German with Ein and Aus for on and off on the power supply and Fein and Grob for fine and coarse below the tuning knobs.