Variable speed belt gear motors are space-saving, continually adjustable drives. In the standard edition the central adjustment is manufactured with a hand wheel. Unlike inverter procedure the electric motor power remains continuous and the torque increases if the speed of the engine drops.
The variable speed gear unit housing has a Variable Speed Belt Gear Motors Speed Reducer Gearbox confirmed symmetrical design. The adjusting pulleys possess a wedge formed symmetrical cross section with low mass. The form of the pulleys guarantees uniform flank pressure and therefore high power transmission, actually at high belt rate.
The effect is optimal control 
behaviour with uniform distribution of forces and minimal energy consumption.