A bumper having a hollow section and attached to it mounting brackets for attaching the bumper to a vehicle\u2014in particular on longitudinal beams of a private car\u2014is such that section walls that are spaced apart form a compression strut and a tensile strut and a pair of flanking walls joining the said struts make up the hollow section. A cartridge memory interface device includes processing circuitry adapted for reading cartridge usage data from a memory element of an imaging cartridge. A simple sensor is attached to a pipe for measuring the vibration and is connected to a processing unit via wired connection. The distribution of the grating periodicity is asymmetric around a central reference section.