NOVELTY - The device (11) has a mass (3) movable along a degree of freedom relative to connection interface (7) that connects the device to a vibrating support (2). A spring (4) exerts a return force between the mass and the interface. A detection unit detects movement direction of the interface along the degree of freedom. A coupling unit (6) couples the mass to the interface when the movement direction of the interface is opposite to that of the mass, and uncouples the mass from the interface before a change in the interface direction and when the interface direction is similar to that of the mass.    USE - Pseudo-resonant micromechanical device for amplifying vibrating motion of a vibrating support e.g. machine or vehicle, of a system (claimed) such as resonant system, for converting the vibrating motion into electricity.    ADVANTAGE - The coupling unit couples the mass to the interface when the movement direction of the interface is opposite to that of the mass, and uncouples the mass from the interface before change in the interface direction and when the interface direction is similar to that of the mass, thus enabling the vibrating support to increase the kinetic energy of the mass, even when the vibration frequency exceeds from the resonance frequency of the mass and the spring, and hence providing high kinetic energy to the mass over a wide range of vibration frequency, while conserving the compactness of the device.    DETAILED DESCRIPTION - The interface, the mass and the spring have a common unitary element formed in a silicon substrate. INDEPENDENT CLAIMS are also included for the following:    (1) a system comprising a vibrating support whose weight is fifty times higher than that of a micromechanical device    (2) a method for amplification of motion of a vibrating unit by a micromechanical device.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a micromechanical device for amplifying vibrating motion of a vibrating support.    Vibrating support (2)    Mass (3)    Spring (4)    Coupling unit (6)    Connection interface (7)    Resonant system (10)    Pseudo-resonant micromechanical device (11)