Abstract: A resonant loop current disturbing probe. This probe comprises a conductive loop closed on a photoresistor, a light-emitting diode optically coupled to the photoresistor by an optical fiber and a diode control circuit. This probe is characterized in that it also comprises a variable capacitor connected in parallel to the loop. The loop-capacitor assembly forms a resonant circuit, the capacitor being adjusted in such a way that said circuit resonates at the frequency of the current to be disturbed. Application is to the measurement of the current in antennas.

Abstract: The invention relates to a process for the transmission in blocks of digital information words with a correction capability. This process consists of transmitting in blocks digital information words, each information word having a length of n.sub.1 bits, in which with each sequence of n.sub.2 -k (n.sub.2 >k) of consecutive information words are associated k redundancy words of n.sub.1 bits each in which, for each order i (1<i<n.sub.2), the k bits of order i of the redundancy words are redundancy bits in accordance with a Hamming code (n.sub.2 0k, k). For each set of n.sub.2 linked words, each word is transmitted while being protected by an error detecting code. Several sets of linked words can be interlaced. The words of the same order or rank of each set form a group and the groups can be formed by frames.

Abstract: A process for regenerating a periodic signal creates two signals. The first ignal provides for the detection of a periodic signal for a short time preceding the theoretical timing position of the periodic signal. The second signal is transmitted a very short time after the theoretical timing position of the periodic signal and serves as a substitute periodic signal, when the periodic signal has not been detected prior to a transmission of the second signal. The circuit, used to receive broadcasted digital data, is comprised of a counter (L), a D flip-flop (B1) and a clock (CLX) having a frequency which is equal to a multiple of the data bit rate which is to be received. The counter (L) has an initializing input connected to the Q output of the flip-flop (B1). It has two outputs (X, Y) corresponding to the transmissions of the first and second signals.

Abstract: A multiple printing head, having k print points responds to binary samples hich represent a grid of points, that are continuously repeated. The m horizontal lines correspond to television lines, each line comprising n points.The vertical lines formed by the grid points are grouped to form n/k columns, each comprising k vertical lines. The point bits are transmitted to the printing head by the point bits of the first line and the last column, then by the point bits of the second line and the last column, and so on up to those of the m.sup.th line and the last column. The point bits of the first line and the last but one column are transmitted to the said printing head, then those of the second line and the last but one column, and so on up to those of the m.sup.th lines and the last but one column, then the actual support is again shifted as previously. Those transmission operations for the point bits, interrupted by head shifts, are repeated column by column up to print the points of the m.sup.

Abstract: A process for scrambling and unscrambling the image part of a sampled MAC ne video signal excluding the synchronization signal begins by dividing at two dividing points the MAC luminance signal and the chrominance signal to form two pairs of segments that are adjacent in each pair. For both transmission and reception each one of two dividing points between the two segments is synchronously defined in a pseudo-random manner to form a pair slightly overlapping in the neighborhood of the pertinent dividing point. The segments are processed in each pair as a whole in order to scramble prior to transmission and again to unscramble upon reception so as to restore the initial video signal.

Abstract: A receiver is provided for a television system which uses time division miplexing (TDM) of analog image signals and of bursts of duobinary coded digital data signals. The digital data signals are transmitted during the line and frame blanking intervals and grouped together in packets, comprising the sound and synchronization signals, the spectral width required by the analog part being greater than that required by the digital part. The receiver comprises a common frequency demodulator for the analog and digital signals, adaptive as a function of the signal-to-noise ratio after demodulation as a width less than the width which is optimum for the analog part when the latter has a high signal-to-noise ratio. The demodulator has an input filter which is either analog or digital and may be adjusted in response to the error rate.

Abstract: A system for transcoding signals for a 12.times.10 dot matrix into signals for a 8.times.10 dot matrix uses a two phase conversion process. In the first phase, the pixels of each line are arranged in groups of three and in their natural order. Each group of three pixels is logically processed to obtain a group of two converted pixels. In the second phase, the configuration of the initial four pixel block which straddles the limit or interspace between two three-pixel groups are analyzed. Depending on the difference found during the analysis, the two pixels which are converted in the first phase are kept on either side of the limit, or are replaced by either the corresponding converted pixels of the former line or the pixels that are calculated in the second phase.

Abstract: In a broadcasting system with time division multiplexing of digital signals containing a synchronization pattern and analog signals, sync extraction is achieved with a process including detecting the extreme values of the signals to be subjected to decoding, after they have been amplified with a gain G, with a time constant compatible with the low cut off frequencies to be accomodated; the gain G is controlled as a decreasing function of the difference between the extreme values with a time constant greater by several orders of size than the repetition period of the multiplex; before decoding and determination of the extreme values, there is added to the amplified signal a DC component which is a decreasing function of the sum of the extreme values, until the retrieval of the clock signal and identification of the synchronization pattern downstream of the coding.

Abstract: Echo cancellation is carried out on a received demodulated analog signal. The apparatus comprises an analog transversal filter, a computing circuit for generating the direct coefficients a1 to ar and, eventually, feedback coefficients b2 to bm of an analog transversal filter. The input of a computing circuit is connected to the input of an analog transversal filter. The computing circuit is comprised of an analog-to-digital converter, whose output is connected to a self-adaptive digital transversal filter. The values of the digital transversal filter multiplication coefficients are applied, as coefficients, to the multipliers of the analog transversal filter. The optimization criterion is that of the mean quadratic error. The convergence algorithm is that of the gradient. The iterative correction may be carried out at each step on the digital transversal filter's group of coefficients. Or, it can be carried out cyclically of each of the digital transversal filter's coefficients.

Abstract: The digital circuit is for receiving a master clock signal at a frequency te f on an input and delivering a rectangular shaped output signal at a lower frequency (M/N)f where M is an integer and N is an even integer greater than M. The circuit comprises an even number N of series connected flip-flops in a ring arrangement, each flip-flop being connected to receive input signals from the preceding flip-flop and from the following flip-flop and to receive a master clock signal on a clock input. The even numbered flip-flops are of a type different from the type of the odd numbered flip-flops. The outputs of the flip-flops each deliver a rectangular pulse signal having a duty ratio equal to 1/N of that of the master clock signal. The pulse signals are applied to a combination logic of OR type giving an output signal combining the outputs of said plurality of flip-flops.

Abstract: A digital data pack transmission system is especially--but not exclusiveluseful in videotex or teletext transmission (i.e. videotext or teletext data is transmitted during intervals between segments of video signals). The inventive system uses a continuous transmission carrier. A plurality of data packs are individually included in each block of data which is periodically transmitted. Dummy packs are used to fill the blocks, if less than a full complement of packs is required. The time periods available for the transmission of blocks of data are exactly equal to or a little longer than the maximum length of the transmitted blocks. The beginning of each data block has a synchronization bit pattern which is constituted by a "bit sync" byte followed by a "byte sync" byte. Except for the synchronizing pattern, the signals are scrambled before transmission and descrambled upon receipt and recognization of the data.

Abstract: A radio system broadcasts binary data packets that can be received in mob receivers. The initial parts of the packets are transmitted periodically. The prefix of each packet includes synchronizing information. The synchronization processing includes seeking a phase and a tracking phase. The transition from the seeking to the tracking phases occurs when the synchronization pattern has been received two consecutive times with a null Hamming distance.

Abstract: The circuit comprises a surface acoustic wave device. On the substrate (32) f the surface acoustic wave device, are provided two pairs of input transducers (33, 34, 35, 36) connected, in parallel, to the input of the circuit. The transducers (33, 34, 35, 36) initiate surface acoustic waves corresponding to the signals applied on two pairs of paths (41, 42, 43, 44) ending at two pairs of reception transducers (37, 38, 39, 40). The outputs of the output transducers of the first pair (37, 38) are connected to the two inputs of a mixer (28) whose output yields the received digital signal. The outputs of the second pair of transducers (39, 40) are connected to the inputs of two limiters (26, 27) whose outputs are connected to the two inputs of a mixer (29) whose output yields the analog signal.

Abstract: A videodisc reader head positioning control system stores the keyed-in address for a desired picture frame and compares it to the track address for the frames during passage of the reader head toward the desired frame. Logic circuitry distinguishes the difference between the desired address and the address of the head's current position in order to control the head positioning unit at a fast, intermediate, or precision speed. Upon reaching the desired address, the logic circuitry maintains the position of the head for stop frame display of the picture information.

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: 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: In the disclosed teletext system, the transmitter station broadcasts data cks data from several channels, the data packs being time multiplexed. Each data pack comprises a prefix signal for causing a teletext receiver either to accept the data packs of a selected channel or to reject data packs from other channels. In addition to the prefix, and possibly page flags followed by page numbers and row flags followed by row numbers, the sequence of eight-bit words, transmitted in a pack, may comprise escape eight-bit words followed by type identity eight-bit words, which are themselves followed by a sequence of characters to be displayed in the same type the identity of which is determined by the preceding type identity eight-bit words.