Abstract: According to this invention, a field of useful data is split into a number of basic entities, called "data groups". Each data group is, in turn, split into smaller basic entities or "data blocks". Each resulting data block is inserted in a data packet to be transmitted through a teletext or videotext network. Therefore, an input coupler has two functional parts: a data group generator and a data packet generator.

Abstract: A videotex asynchroneous transmission system uses a parity bit for each character, with a continuous ARQ-type retransmission method. The data are transmitted in blocks (so-called "code words"). Each code word is comprised of a block of seventeen bytes "1"-"15" constituting the characters which are to be transmitted encoded by seven bits b1-b7. The 8th bit b8 of each byte is the parity bit. The 16th byte is the check byte of the code word, and the 17th byte being the enabling byte of the code word.

Abstract: An image memory graphic terminal comprising an image memory constituted by memory planes, each plane incorporating a matrix system of memory points, a sequencer, a graphic display processor, a video signal generator, a video display receiver, a management microcomputer.According to the invention, the terminal also comprises a system for writing or recording in the image memory image texture signals, said system comprising(A) a circuit for processing the access cycle to the image memory, said circuit incorporating:(A.sub.1) a circuit for the transmission, with a time lag, of the signals for controlling the access cycle to the memory,(A.sub.2) a shaping circuit (42),(B) a circuit for the determination of the word to be written into the memory, incorporating:(B.sub.1) an operation parametrization circuit,(B.sub.2) a computing circuit being able to: . calculate two coordinates .alpha.* and .beta.* from addresses x, y and signals .DELTA.X, .DELTA.Y, .DELTA.H, .DELTA.V, off.sub.x, off.sub.y(B.sub.

Abstract: The structure of an access point to a data packet broadcasting network comprises a plurality of couplers (Cx), a buffer memory (MTP) and a central control unit (MPC) interconnected by a main bus (MB). Each coupler (Cx) is connected to a plurality of data sources. The buffer memory (MTP) is connected to a transmission equipment of the data packet broadcasting network. Each coupler (Cx) includes a dual access (MCx), a microprocessor (MUPx), a read only memory (ROMx), a plurality of access circuits (CAS1-CAS4 and CAP1-CAP4) each connected to a data source, a local bus (Bx). In each coupler there is stored, in addition to the coupler control software, a set of subroutines for exchanging information with the buffer memory (MTP).

Abstract: A TV receiver is adapted to display either the regularly broadcast video signals or videotext information. The video signals contain their own internal synchronization signals. The videotext information requires locally generated synchronization signals which may be used to replace the normal video internal synchronization signals. The invention provides means for switching between the normally broadcast and the internally generated synchronization signals.

Abstract: A numerical or digital transmission system uses an adaptative coding, of log information, which is sampled and transformed by an orthogonal transformation. The coding has a rate of data flow or delivery, which is reduced by orthogonal transformation with an adaptative threshold. In each scanning field, the binary elements of the coefficients are obtained by a basic coding with a quantification pitch 2S, (S being a whole number either positive or null). A complementary coding is transmitted. The complementary coding is obtained by adding binary elements of weights 2S-1 for each one of the coefficients, until the transmission capacity of the channel is filled. The coefficients are taken in chronological order. The invention is applicable to digital television, but also the coding may be used for transmission of high fidelity sound.

Abstract: A digital signal formed from successive words representing quantized samples of sound information and comprising silent periods is synchronized with a local reading clock. For that, the words are stored in a random access memory as they arrive, they are read at the frequency of the local clock and the filling rate of the store is permanently determined. A comparator compares this rate with a given range. If the filling rate is greater than a maximum threshold or less than a minimum threshold, the contents of the memory are modified at the first silent interval which appears.

Abstract: A digital signal of n-bit words N.sub.i is enciphered into an enciphered signal of n-bit words R.sub.i. In an enciphering unit, a logic circuit delivers each enciphered word R.sub.i through a logic operation g performed on the word N.sub.i and on an n-bit, stored, enciphering word P.sub.i-l. An addressing circuit formulates an address word A.sub.i-l having a bits fully or partly belonging at least to the preceding enciphered word R.sub.i-l. A memory of 2.sup.a predetermined P.sub.i-l words is read by each address word A.sub.i-l to supply a corresponding word P.sub.i-l to the logic circuit for it to perform the g operation such that R.sub.i =g(N.sub.i, P.sub.i-l). A deciphering unit receives the enciphered words R.sub.i for formulating the address words A.sub.i controlling reading of the corresponding words P.sub.i out of 2.sup.a stored words. Each deciphered word N.sub.i is obtained by a logic operation h, referred to as contrary to g, performed on the enciphered word R.sub.i and on the stored word P.sub.

Abstract: The invention relates to a scratch pad memory system having a table of contents for identifying program material recorded on a magnetic tape in a cassette or cartridge with program material being recorded or changed responsive to user command. The scratch pad memory system comprising an address register, a read only storage, and having an interface for read/write storage and a text displaying terminal coupled to a television receiver for display of program material.

Abstract: To obtain a duo-binary FSK modulation, the modulating binary signal train has a three state partial response and is fed through a precoding, a transition-type coding, a simplified MSK modulation at the carrier frequency, a frequency division by two, and a multiplication by the same signal delayed by one binary element period. In order to obtain a "tamed FSK" modulation, the modulating binary signal train has a five state partial response and is fed through precoding, a transition-type coding, a simplified MSK modulation at the carrier frequency, a frequency division by two, a multiplication by the same signal delayed, for one part, by one binary element period and, for the other part, by two binary element periods. A TFM modulation is obtained by using the FSK duo-binary generating process, but a wave shaping filter is connected between the division by two circuit and the multiplication circuit.

Abstract: The invention relates to doublet plates and the method of making them so t they may operate at very high frequencies.

Abstract: The present invention relates to a device for the digital transmission and display of graphics and/or of characters on a screen, the device comprising a terminal connected to a transmission network, to a graphic acquisition device and to a unit for display on a screen. Each terminal comprises a storage unit which, according to the invention, comprises a plurality of storage assemblies validatable in parallel, each storage assembly comprising a circuit effecting a logic combination between an input word and the word already written at the address indicated. The invention is more particularly applicable to the production of telewriting systems or of combined systems of telewriting and videotext (viewdata).

Abstract: A system broadcasts videotext data in the form of data packets originating from numerical data coming from several paths. Each packet has a prefix which contains synchronization and path identification code signals, a format signal which indicates the length of the data which follow the prefix. The transmitting station has as many coupling devices as there are paths for originating data. The coupling device has a data memory coupled to drive to a multiplexing circuit under the control of a common governing circuit. An inhibition order is given either as soon as the memory is full, or as soon as a counter has reached a pre-determined count. Then, the memory is connected to the multiplexing circuit, into which the stored data is emptied. The system is characterized in that a small capacity buffer is used between the memory and the input circuit for reading data out of the buffer memory responsive to a programmer. A transcoder treats the broadcast data to fit it into the system format.

Abstract: The consequences of the loss of a packet are attenuated in a digital data communication apparatus using packet switching by structuring the digital data as multibit words into frames having a fixed length l and assembling the frames into packets all having the same predetermined length L=kl, where k is a predetermined integer. Continuity index words incremented by one each time a new frame or packet is assembled may be located into the frame locking word or the packet prefix. Then the number of packets which are lost may be determined at the receiver location by monitoring the successively received index words. When the digital data represent successive samples which are correlated, for instance when such samples represent a sound, substitution data may be generated at the receiver location and used in place of the missing data.

Abstract: Television system using a marking code superimposed on a picture.According to the invention, this code is constituted by a strip located in the right-hand part of the picture and formed by a periodic sequence of white and black areas constituting a clock and by a strip located in the left-hand part of the picture and formed by a sequence of white or black areas constituting the actual code. A decoder detects the presence of clock signals and compares the code received with stored codes.

Abstract: A device for following and recursively estimating the local state of pict contours defined by lines of N points distributed in accordance with an orthogonal sampling structure, said points being defined by successive numerical samples.The invention also relates to a differential coded pulse modulation coder and a differential coded pulse modulation decoder.

Abstract: A television signal noise reduction system employs a movement detector for automatically selecting one of three parallel processing paths, the first of which passes the video signal without modification and the other two of which calculate different weighted averages of the current pixel and surrounding pixels from the current frame and the previous frame.

Abstract: A television system with access control comprises a transmitter and receis. The transmitter comprises a video signal and sound signal formation circuit, means for transmitting these signals and a jamming circuit using a service key. Each receiver comprises means for receiving the transmitted signals, means for the display of the picture and for restoring the sound and an unjamming circuit connected to the reception means and working with the service key.It also comprises a subscription management center and in the transmitter a digital signal generator, a circuit for the formation of digital messages and a data broadcasting system and in the receiver a subscription card, an extraction circuit for the data, and a circuit for restoring the service key. There is also at least one subscription card loading station connected to the subscription management center.

Abstract: A subscription card for videotex receivers, comprising:(a) a support,(b) means for processing the information, comprising in particular a control unit governing an arithmetical and logical unit and a live memory,(c) an interface permitting exchanges between the card and the apparatus in which it is inserted (charging station or receiver), further comprising:(d) a programmable memory comprising a plurality of locations for receiving numerical subscription blocks C.sub.i,(e) a dead memory containing instructions for proceeding with the recording and selection of said subscription blocks, and for carrying out a calculation,(f) a calculation circuit receiving, from the receiver in which the card is inserted, numerical messages M.sub.i and receiving from said programmable memory a numerical subscription block C.sub.i, this circuit being adapted to work out an algorithm whose parameters are provided by the subscribers' keys C.sub.

Abstract: In the error signal feature sensor of the device, an analog synthesized signal is produced throughout the first portion of each period of the analog noisy test signal to be acquired by means of the digital value of samples memorizing in a random access memory and a digital-to-analog converter. The noisy signal and the synthesized signal are compared therebetween at predetermined sampling times in predetermined number. The sign and modulus of the error signal in relation to a predetermined threshold voltage are written in the memory. During the second portion of the period without the noisy signal, a processing unit as a microprocessor calculates the new digital values of the samples in term of comparison results and the preceding digital values of the samples in accordance with a particular algorithm. A new comparison and calculation cycle is performed and so on.