Belt and Pulley Mechanism Animation for Rotary to Linear Motion

Belt and Pulley Mechanism
Belt and pulley combination is used to convert rotary to linear motion. The belt is connected to the carriage on both ends as shown in the animation. The closed loop thus formed runs over pulleys placed on either ends. One of the pulleys is connected to an electric motor and the other on the opposite side is idler pulley for supporting the belt. When the driving pulley is rotated, the belt pulls the carriage in the same direction according to the direction of rotation of the driving pulley. The carriage can be moved in either direction by controlling the direction of rotation. For reliable and slip less transmission cog belts are used and the pulleys are replaced with suitable cog wheels.

[barhacohen]

What if I want this mechanism but with two carriages? I want the carriages to be moving in opposite directions, so essentially I need each carriage to be attached to opposite sides of the belt (one attached to upper, one attached to lower). Is this possible using 1 rail? Or would I have to use two rails?

If this mechanism exists somewhere, I'd appreciate you telling me how to find it/how to to implement it.