A reduction drive is a mechanical gadget to shift planetary gearbox rotational speed. A planetary decrease drive is a small scale version using ball bearings in an epicyclic arrangement instead of toothed gears.
Reduction drives are found in engines of all types to increase the quantity of torque per revolution of a shaft: the gearbox of any car is a ubiquitous exemplory case of a decrease drive. Common household uses are washers, meals blenders and window-winders. Decrease drives are also used to decrease the rotational acceleration of an input shaft to an appropriate output speed. Reduction drives can be a gear train design or belt driven.
Planetary reduction drives are usually attached between the shaft of the adjustable capacitor and the tuning knob of any radio, to allow good adjustments of the tuning capacitor 
