Abstract: A plasma ignition device for internal combustion engines is described. It comprises a driving and analog and/or digital control unit, an ignition coil and a spark plug, interconnected each other in a circuit by means of electrical/electronic connection means. The ignition coil comprises two primary windings connected in series each other, having a central electrical connection between the first primary winding and the second primary winding, for electrically charging a capacitor, connected in series to the two primary windings, and for magnetically charging a magnetic core magnetically coupled to a secondary winding of the ignition coil, in order to generate a potential difference across a discharge “gap” of a spark plug.

Abstract: The internal stress state of a plate of heat tempered plate glass is tested by means of a device which uses a source of polarized monochromatic infrared radiation. This radiation passes through the glass in a point, and the variation of the polarization state is determined by means of an analyzer with the polarization axis at 90.degree. with respect to the polarizing filter.