Geared steam locomotive
This gearing is part of the machinery within the locomotive and should not be confused with the pinion that propels a rack locomotive along the rack between the rails. The geared steam locomotives that have been built have been for conventional track, relying on the adhesion between wheels and rail.
Reversing gear
The development of articulated locomotives was a major impetus to the development of power reverse systems, because these typically had two or even three sets of reverse gear, instead of just one on a simple locomotive. The Baldwin Locomotive Works used the Ragonnet reversing gear, and other American builders generally abandoned positive locking features. In British use, locking cylinders remained in use. The Hadfield reversing gear, patented in 1950, was in most particulars a Ragonnet reversing gear with added locking cylinder.
Most Beyer Garratt locomotives used the Hadfield system.
Many American locomotives were built, or retro-fitted, with power reverse, e.g. PRR K4s, PRR N1s, PRR B6, PRR L1s.