ComInTec's expandable-disc pulleys are the most simple and economic solution for changing rapidly and continuously the rotational speed of two shafts without having to stop the power transmission. ComInTec's pulleys can be variable center distance, where the two plates slide symmetrically on the hub, transmitting motion to a fixed driven pulley with variation ratios up to 1:3.5 by adjusting the distance between the centers of the two pulleys. They can also be fixed center distance, where a pair of pulleys both have a single mobile disc that makes it possible to vary the speed with a ratio of up to 1:12.3 by adjusting the mobile disc on the driving pulley with a handwheel.