What does a parallel motion linkage achieve?

A parallel motion linkage is designed to convert the input motion into an output motion that maintains the same direction and distance, providing an identical parallel motion. This mechanical linkage is commonly used in applications like drawing boards and pantographs, where it is crucial to maintain the alignment and proportionality of the movement. The system allows for the effective transfer of force, ensuring that when one part of the linkage moves, another part moves in exact parallel, thus achieving the intended outcome without altering the nature of the input motion.

The other options suggest variations or alterations in motion that do not represent the fundamental purpose of a parallel motion linkage, which is to keep the motion parallel and consistent.