The rotation rate of the motor shaft is synchronized to the utility frequency; 60 cycles per second (Hz) in North America and parts of South America, 50 cycles per second in most other countries. The gear train scales this rotation so the minute hand rotates once per hour.
The text describes how the rotation of a motor shaft is synchronized with the utility frequency (60 Hz in North America and parts of South America, 50 Hz in most other countries) to drive the minute hand on a clock. The gear train scales this rotation to ensure that the minute hand moves once per hour.