Reverser

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Reverser is a control device, typically a lever, used to set the moving direction of a motorized rail vehicle – forward, reverse or neutral. The latter typically separates the wheels from the powertrain altogether. Reverser should never be operated when a vehicle is in motion, to avoid catastrophic damage to the powertrain. For the same reason, throttle and dynamic brakes typically need to be disengaged for the reverser to be operable.

On steam engines, the equivalent of the reverser is called cutoff. It is a bit more complex in that it determines the steam intake duration per cylinder cycle.