Abstract: Process for testing transparent material webs, particularly plate glass ribbons or the like, for material defects, in which the glass ribbon or the like conveyed in its longitudinal direction is scanned over its width in a scanning plane at right angles to its conveying plane and direction by means of a laser-produced flying light spot, the forward and back scattering produced by the inclusions is measured in each case one detection plane sloping with respect to the scanning plane, electrical signals are derived from the measured values obtained and said signals are processed for material defect identification, characterized in that a laser operating in the near IR-range is used as the light spot source, as well as apparatus for preforming this process.

Abstract: An electrically heatable self-defrosting windshield has a transparent panel, two low-resistance groups of wires embedded in the panel and defining a primary zone requiring rapid heating, and at least one high-resistance group of wires embedded in the panel and defining a secondary zone adjacent the primary zone and not requiring rapid heating. A switch connected to the wire groups and to an electric power source is movable between a fast-heat position connecting the two low-resistance groups in parallel with each other across the source and effectively disconnecting the high-resistance wires, and a slow-heat position connecting the two low-resistance groups in series with each other and jointly in parallel with the high-resistance groups across the source. The total resistance of the groups in the fast-heat position is generally the same as in the slow-heat position.