Abstract: The disclosure is a stepped rectification high-voltage transformer including a secondary step-up winding in which at least two output diodes connected to two different stages of this secondary winding are located in a same axial level and perpendicular to the potentiometer block forming part of the insulating casing. The invention is applicable notably to the power supply of television cathode ray tubes.

Abstract: The disclosure relates to a device for illumination of a screen, notably a liquid-crystal screen. It includes a light integrator that receives a light beam from a source and outputs an illuminating beam for the screen. The light integrator makes use of lenses, but has no lenses in the parts of the beam where the energy flux is weak, which enables more uniform illumination of the screen. To improve the contrast of the illumination of the liquid-crystal screen, the whole illuminating beam is directed onto the screen at an angle to the optical axis of the system. The invention is applicable to liquid-crystal screens.

Abstract: A scan frequency detector is responsive to a horizontal synchronization signal to generate a data signal that is indicative of the horizontal scan frequency. A digital-to-analog (D/A) converter produces from the data signal an analog, output signal at a first level, when the horizontal frequency is within a first range of values, at a second level, when the horizontal frequency is within a second range of values and at a third level, when the horizontal frequency is within a third range of values. A first switch of a switched S-capacitor arrangement, is turned on, when the output signal is at the first level. The first switch and a second switch of the switched S-capacitor arrangement, are turned on, when the output signal is at the second level. Both the first and second switches are turned off, when the output signal is at the third level. The third and second levels are distinguished by a level detector that includes a zener diode.

Abstract: The disclosure relates to a recording and reading apparatus constituting a kind of video reservoir in the home of the consumer. Thanks to a large-capacity storing technique with suitable technical device, broadcasters transmit numerous programs via specific channels and the consumer may control the content of his reservoir (by recording, reading and erasing programs). The invention is applicable to on-demand video in the consumer's home with a video reservoir constituting a video-library that is regularly updated by broadcasters and/or by the consumer himself.

Abstract: The invention relates to a conditional access system making it possible for a service provider to supply his services solely to users having acquired entitlements to these services.The services supplied by a service provider consist of an item scrambled by control words. To keep these control words secret, they are supplied in messages (MEC) after having been encrypted with an encryption algorithm with key K.According to the invention, one and the same message (MEC) contains the same control word (Cwi) encrypted several times, each encryption (E(Cwi)Kj) of the control word depending on a different encryption key (Kj).The invention applies to any type of conditional access system, be this system either of "off-line" or "on-line" type.

Abstract: An optical polarization device includes a source of light emitting a non-polarised light beam. A polarization separator reflects one polarization component of the light beam and transmits the other polarization component. A reflection means receives the component reflected by the polarization separator, rotates its polarization plane through 90.degree., and returns it to the polarization separator. The polarization separator is a plane element. The reflection means is positioned on the source side of the separator and consists of a regular network of prisms, each partially covered with a reflective layer associated with a .lambda./4 plate.

Abstract: Disclosed are a method for the control of an image display screen displaying half-tones and a display device implementing this method. The disclosed method is used to control an image display screen of the type having cells arranged in rows and columns and working either in a state known as an "OFF" state or in a state known as an "ON" state in which they are activated and produce light. The method consists in activating the cells of each row during sub-periods of different duration, with orders of distribution of the sub-periods that are different between two successive rows. This results in a reduction of the amplitude of the variations of a load constituted by the cells in the <<lit>> state of these two consecutive rows. Application inter alia to alternating plasma panels.

Abstract: Known LCD projectors, used for example in TV sets, can only be manually adjusted for the compensation of the changing color spectrum of the lamp due to its aging process. An LCD projector according to the invention further comprises an image sensor to measure the light intensity of the lamp. In a color adjusting circuit the image color is compensated as a function of the measured signal by controlling the LCD valve.

Abstract: A speech based man-machine communication system is given, comprising more than one controllable device provided with speech synthesis function. Each of the devices in question is provided with its own unique voice pattern. The devices are connected via a bus, so that a central authority handles all the requests from the user. Because the user uses his natural language, commands can be ambiguous. Therefore an algorithm for handling ambiguous situations is provided.

Abstract: The conditional access system of the present invention allows a service provider to supply services, which may be scrambled by a control word, only to those users who have acquired entitlements to these services. The control word is supplied in Entitlement Control Messages (ECM) after having been encrypted using a key. The entitlements of each user are forwarded in Entitlement Management Messages which contain the key. The conditional access system verifies and validates the ECM and EMM prior to processing the control word.

Abstract: A method for the control of a display screen whose pixels are cells producing light is used to minimize certain image defects known as excess brightness defects caused by major variations in the number of cells activated. For this purpose, the invention operates on the sub-division of the activation times of the cells during a given cycle time to reduce a time during which cells, selected as a function of their luminance level, are the only ones to be activated. The disclosed method can be applied especially to the control of alternating type plasma panels.

Abstract: The invention relates to a process for data certification as well as to the system implementing the certification process.The certification of the data is performed by scrambling.An authority independent of the entity which controls the data source and of the user(s) for which these data are intended, scrambles the data with the aid of control words and encrypts the control words with the aid of an encryption algorithm with key K.So that a user or the users can descramble the data scrambled by the independent authority, a certification verification device containing the encryption key K is supplied to the user or users under the control of the independent authority.The certification process and the system associated therewith apply more particularly to conditional-access systems.

Abstract: A process for selecting events, especially television programs and device and graphical interface implementing this process, including a transmission of service information. According to this process, at least two one-dimensional parallel lists of items are displayed, the first list of items (3) containing events, the second one-dimensional list of items (2) containing at least one function for filtering events and/or at least one function capable of acting on said events. The process furthermore includes the step of picking out selected items, a single item being selected from each list, another item being selectable from a list simply by placing a single cursor over said other item, a selected item remaining selected when said cursor is moved off the list containing this selected item.

Abstract: The present invention relates to a backlight system for transmissive electro-optical modulator comprising: at least one source of light rays; at least one reflector for returning the light rays along a first direction referenced z; a means of transmission of light, positioned at the exit of the reflector in such a way as to transport the light rays along the z direction, one of the faces of the transmission means lying along the z direction comprising a micro-prismatic structure which specularly reflects the light rays and extracts them from the transmission means substantially along a second direction referenced x perpendicular to the first direction and a collimation means (20) situated between the source of light rays and the transmission meansz. The said collimation means (20) comprises an entrance face (21) inclined with respect to the first direction referenced z. The invention applies more particularly to retroprojection.

Abstract: The invention is a process and apparatus for estimating a bit budget in a circuit for compressing digital data, especially digitized television signals. Signals represented by N-bit coded samples, are estimated based upon the probability of a bit of given order having a given value (0 or 1) out of M binary words representing M samples of the signal. An entropy calculation is performed on the basis of the probabilities corresponding to the N bits with the sum of all the entropies corresponding to the desired estimate.

Abstract: The system includes a plurality of decision units, at least one verification unit, and at least one counting unit, the units being functionally and structurally separate from each other. Each decision unit includes means for producing a source information item and an identity information item, and means for enciphering this source information item in such a way as to render it essentially indecipherable by the verification unit but decipherable by the counting unit. The verification unit includes a file which includes the identities of the decision units, means for checking the identity of the decision unit from which an incoming message originates, and means for compiling an anonymous derived message which is essentially devoid of any identity information item decipherable by the counting unit.