Centrifugal brakes or overspeed brakes are employed in a wide variety of applications including:
Controlled descent of personnel from buildings in an emergency, overspeed brake control of wind generators to prevent structural damage, automatic control of vehicles down slopes (eg. lifeboat launching), automatic descent control of service platforms and overspeed control of revolving/sliding doors.
The photograph shows an overspeed brake connected to a single stage speed increaser gearbox. The source speed of c.200rpm was too low to allow a cost effective centrifugal brake solution so the speed is increased through the gearbox to c.1400rpm (1:7 ratio).