Techniques and apparatus for causing electromagnetic interaction between an oscillator and a quantum ensemble with transition moments to transfer energy. The rollers tapered to the angle are mounted on the roller shafts and oriented with the tapering inwardly to the main shaft thereby providing each roller with a bottom region of its tapered surface being perpendicularly oriented with the axis of the main shaft. A hysteresis of the pedal characteristic curve is produced and is independent of the additional restoring force of the electromechanical actuator.