An alternative to the oscillating agitator design is the impeller type washtub pioneered by Hoover on its long running "Hoovermatic" series of top loading machines. Here, an impeller (trademarked by Hoover as a "Pulsator") mounted on the side of the tub spins in a constant direction, and creates a fast moving current of water in the tub which drags the clothes through the water along a toroidal path. The impeller design has the advantage of its mechanical simplicity - a single speed motor with belt drive is all that is required to drive the Pulsator with no need for gearboxes or complex electrical controls, but has the disadvantage of lower load capacity in relation to tub size. Hoovermatic machines were made mostly in twin tub format for the European market - (where they competed with Hotpoint's "Supermatic" line which used the oscillating agitator design) until the early 1990s. Some industrial garment testing machines still use the Hoover wash action.