Electric generator is disclosed having a stator and a rotor. The invention further relates to retroreflective sheeting. Two transmission ratio ranges differ from each other through the transmission ratio of an input shaft of the parallel gearbox and its output shaft. In either case, cyclical changes in the integrals of the individual cardiac cycles are tracked. The system and method also apply at least one diffusion gradient to the ROI to modulate the first MR parameter with a second MR parameter, acquire MR data from the ROI, and reconstruct a parametric map of the ROI using the MR data, wherein the parametric map is weighted based on the first MR parameter and modulated by the second MR parameter. In the extended position, the braking elements make braking contact with the contacting structure.