An input device in a vehicle and a method for occupant classification, in which an input regarding occupant classification is requested from the driver or some other user. The textual term may be related to one or more users of the social-networking system. During an operating phase, the number of cycles needed to travel through the reference section is determined and a corrected number of cycles per revolution of the exposure drum is determined in accordance with the relationship Kk=K0\xd7MxM0. The autocorrelation sequences may be combined and respiration information may be determined based on the combined autocorrelation sequence.