Abstract: A device for the protection of electric power resistances assembled in a battery using rods, insulating guns and isolators all housed within a dust tight and water jet tight parallelepipedic metallic housing, containing only air for cooling the resistances; fixing screws are provided for assembling and holding the various panels together and seals with a cut-out are provided in all assembly areas between the panels so that electrical continuity between two adjacent parts of the panels is achieved through despite any possible loosening; a compression element is interleaved between two adjacent parts of the panels to be assembled, at right angles to passages for the fixing screws, and the compression element is interleaved between the two adjacent parts for producing on opposite faces of the parts a force greater than the rigidity of the parts and housed in the thickness of the cut-out in the seals providing for contact tightness of the parts of the panels without limiting efficiency.

Abstract: An optical sensor for delivering error signals in order to control focusing of a lens on a movable recording medium or optical memory and more particularly a videodisk comprises a laser for producing a beam which is focused at a point S.sub.1. The divergent beam which proceeds from the point S.sub.1 is reflected from the face AB of a prism and is focused at a point S.sub.2. If the point S.sub.2 is located in the plane of the movable recording medium or so-called memory plane, the beam reflected from the memory plane is autocollimated and passes back through the focusing lens. A part of the beam enters the prism through the face AB, then emerges through the face AC and a circular light spot is formed in the plane corresponding to the circle of least confusion. If the point S.sub.2 is not located in the memory plane, the light spot is deformed and these deformations are detected by four juxtaposed cells placed in the plane of the circle of least confusion.

Abstract: A container for video-discs includes a support for the disc and a protective envelope which is open along one edge to allow the support to be inserted laterally into the envelope. The container comprises furthermore guiding means for centering the video-disc on the support, and means for engaging the support for its handling and insertion means arranged at one end of the support to allow its sliding into the envelope.

Abstract: An apparatus for reproducing information on a flexible video disc in which the disc is accurately positioned facing the transducer head by structure including a fixed plate for prestabilizing the disc in rotation to a substantially constant distance in relation to the lower face of the plate. The plate has a central inlet coaxial with the axis of rotation for providing an air cushion between the disc and lower face of the plate and a rectangular elongated slot extending perpendicular to that axis. A fluid-tight casing houses a transducer head and includes a lower portion extending through the slot for providing a passage for the light beam and for fluid under pressure, the flow of fluid drawing the disc to a distance where equilibrium is established between the forces of attraction and repulsion.