Reverser

A reverser is a device or mechanism that causes a moving system to change its direction or order. The term is used in engineering, transportation, and computing to describe components that reverse thrust, rotation, or sequence.

In railroading, a reverser (sometimes called the reversing gear) is part of the traction system that sets the direction of travel. It controls the polarity or phase to the traction motors, allowing the locomotive to move forward or backward when synchronized with throttle and braking.

In maritime propulsion, a reversing gear engages the propeller shaft so the propeller rotates in the opposite sense, producing reverse thrust. This enables backward movement and precise maneuvering at ports. Modern ships may combine reversers with propeller-pitch control for additional reversing capability.

In aviation, thrust reversers redirect engine thrust forward to aid deceleration after landing. They are installed on many jets and turboprops and are activated on the ground or during touchdown. They reduce stopping distance but are not used during takeoff and have limited effectiveness at high speeds or light weight.

In computing and other fields, a reverser can refer to a software utility or function that reverses the order of data, such as strings or sequences, or a tool used to invert media streams. The meaning depends on context.