T his is a metronome.
Musicians use it as an aid to keep a steady tempo.
A metronome can be adjusted to produce either a faster or slower tempo. A circular dial was probably intended to make it look more attractive. A control should not be designed to look like a dial if it does not work like a dial. The metronome dial should either be removed or should be made to turn to change the number in the display. Home page Metronome photos and idea courtesy of Phil Haine.