摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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. The counting unit includes means for receiving the derived messages from the verification unit, means for processing these messages to compile a statistic of the corresponding source information items, and generating a file of the statistics thus compiled.
摘要:
The disclosure relates to a method of synchronization of clocks wherein, in a system including a digital decoder of a receiver equipped with a sampling clock and a digital encoder of an transmitter also equipped with a sampling clock, said method includes the following stages: in the transmitter, coding by packets of samples of a signal by time intervals of predetermined duration and triggering of the transmission of a data frame when a packet of data is ready to be sent; in the receiver, detection of start of said frame, and generation of a reference signal following said detection, said reference signal being used to correct the clock of the receiver. Another object of the invention is a method of synchronization of clocks wherein, in a system including a digital decoder of a receiver equipped with a sampling clock and a digital encoder of a transmitter also equipped with a sampling clock, in which the transmitter sends frames containing data packets corresponding to a number known of samples, said method includes the following stages in the receiver: reception of a data frame including a packet of data, decoding of said packet and writing of the decoded data in a memory, reading of said decoded data in said memory at a frequency that is a function of the frequency of said clock of the decoder, comparison at a predetermined time of the occupancy of said memory with respect to a threshold, and correction of said clock of the decoder according to the result of said comparison. The invention is applicable in the field of digital transmission, notably transmissions between digital visiophones.
摘要:
A display device having a backlighting system supplying collimated light, a transmissive electro-optical modulator of the liquid crystal display type and a means for distributing the light angularly. The distance between the means for distributing the light angularly and the display is chosen so as to obtain a spatial filtration effect. A layer of colored filters is positioned between the display and the means for distributing the light angularly.
摘要:
The invention is about a dc/dc converter (1) fitted with switching means (11, 12) having a drive electrode (13, 14) each drive electrode (13, 14) being connected to polarization means (49,50). The switching means are to switch on and off a current coming from a direct source of current 2 and circulating in windings (17, 18, 5) of transformers (6, 7) of the converter. The improvement according to the invention comprises a protection circuit 24 connected to means (44) for detecting the value of current circulating in one of the windings (4, 5, 15, 19, 23) of the transformers. Outputs (47, 48) of circuit 24 are connected to the drive electrode (13, 14) of switching means (11, 12). Protection circuit (24) may be a bistable circuit that will lower voltage at its outputs (47, 48) in a permanent way if detected current has been to high, thus switching off in a permanent way switching means (11, 12). The switching off is made in less than a working period of the switching means (11, 12) and prevent any damage to said switching means.
摘要:
The process comprises a "pledging" step in which a debtor party transmits to a creditor party a data item which is the image of a pledged data item, and a "commencement" step in which the debtor party transmits the plain pledged data item to the creditor party who can verify pledge consistency. In the pledging step, the debtor party produces a seed applied to a pseudo-random generator to produce a pseudo-random word, combines this pseudo-random word in a one-to-one and reversible manner with the pledged data item to produce a checkword, and transmits the checkword to the creditor party. In the commencement step, the debtor party transmits to the creditor party the seed together with the plain pledged data item. The creditor party then applies the seed to a pseudo-random generator similar to that of the debtor party to produce another pseudo-random word, combines in the same one-to-one and reversible manner as for the debtor party, this other pseudo-random word with the checkword, to produce a check data item, and checks the consistency of the check data item with the plain pledged data item received from the debtor party.