A process for the certification of a copy of a document, in particular of faxes

摘要

A shock-absorbing device using at least one piston (23) moving in a cylinder (24) filled with an elastomeric gum. The device includes means (29) for altering the cross-section of the mass of gum across the head of the piston (23), particularly according to the travel speed of the piston in the cylinder, whereby the shock-absorption curve of the device may be adapted to the forces to be absorbed. Said device may be used in a variety of fields in which very powerful forces need to be absorbed, e.g. in railway engineering, for protecting constructions from earthquakes, etc.