Abstract: An equipment embodying the invention is designed for bit-level quality check of a digital link in the presence of real traffic. The equipment complies with CCITT recommendations and comprises two checking stations (SP, SS) respectively located at two ends of the digital link (LT) and connected to one another by a service link (LS). First and second check information relating respectively to groups of transmitted frames (MTn.sub.p) and to groups of received frames (MTn.sub.s) are calculated in the stations and comparisons are made in order to detect the transmission errors. The check informations and the frame groups concerned by the transmission errors are transmitted from one station to the other via the service link. Processing circuits are distributed among the stations thereby processing the frame groups concerned by the transmission errors, i.e., analyzing at bit level the errors in the erroneous frames and deriving statistical information and recordings relating to said errors.

Abstract: The device comprises an echo cancelling circuit receiving a first signal and a second signal and a real echo between channels for producing a third signal containing the second signal and a difference between the real echo and the estimated echo. Detectors detect the echo difference and the second signal in the third signal when the level of the third signal exceeds a predetermined threshold. Circuits gain-control the adaptation in the adaptive filtration of the echo cancelling circuit in such a way as to modify the adaptation gain when the second signal is not detected and to prohibit all filtration modifications as long as the second signal is detected. For instance, for an acoustic echo in a telephone set, the echo is not processed when the third signal contains a local speech signal as second signal.

Abstract: A method and device are provided for encoding-decoding an HD digital television signal into a narrow band encoded signal. The HD digital television signal is representative of high definition images sampled at a frequency f1, and the narrow band encoded signal corresponds to a narrow band signal sampled at f2, wherein f2<f1. Narrow band encoding is achieved by horizontal compression by decimation of the image lines of the HD digital television signal so as to bring the number N1 of useful pixels per image line to a value N2=.alpha. of the sampling frequencies, so as to thus form an encoded signal representative of an image line and obtain reduced format high definition images. A narrow band encoded signal representative of digital television signals can thus be broadcast over an HD-MAC NB type channel.

Abstract: The method is founded on the GUAZZO algorithm and is adaptive as it does not require any prior statistical knowledge of source of message to be coded. The message is comprised of a sequence of symbols of the source which are represented by the indication of the direction "0" or "1" chosen at each node of a binary tree. According to the invention, the adaptiveness is obtained by associating with each node two finite-sized counters that count the "0"s and "1"s according to the routing of the tree. The contents of these counters enable the conditional probability of each of the elements "0" and "1" to be estimated at the node.

Abstract: A process for optical transmission by self-heterodyning and a transmission system with a switching matrix using the process. The process consists in transmitting optical signals to one or more receivers of N, from optical transmission means including an optical signal emitting device for modulation by frequency transposition, and an optical fiber connection. Also included in the process is the transmission a given signal on one or more carrier frequencies respectively to one or more receivers, the obtaining of the carrier frequency or frequencies by transposition of an emission frequency by one or more modulation frequencies which are distinct and can be selected as a function of the receiver or receivers, and the transmission of the emission frequency signal on the same optical connection.

Abstract: A communication system is designed to equip an asynchronous time-division network and to enable terminals linked to the network to communicate in the no-connection mode. The system comprises a ring management device and components distributed among the terminals and interfacing the terminals with a virtual ring for managing the production, reception and transmission of data cells. The ring management device is linked via the network to each of the terminals in order to control the connection/disconnection requests coming from the terminals and to supply information concerning cell routing to the terminals linked to the ring. A terminal has a particular role as a pilot for regulating the rate of the data cells in the virtual ring. Another purpose of the pilot terminal is to eliminate the altered cells. Furthermore, there is provided in each of the terminals a device for limiting its rate to a maximum value.

Abstract: In a phase demodulator is received a signal of which the carrier is phase-modulated by a digital pseudorandom sequence itself phase-modulated by a data signal. A frequency close to that of the carrier is locally modulated by a sequence identical to the received sequence. The received and local signals are mixed into a filtered signal with an intermediary frequency band. A repetitive double integration step of the signal filtered into an integrated signal is used and is compared with a threshold in order to quantify the correlation between the received and local signals. Firstly, the local frequency varies according to a few discrete values spread over the uncertainty range of the carrier corresponding to intermediary frequencies in the vicinity of the filtering band. At each discrete frequency value, integration steps are carried out for half-bit local frequency shifts. Synchronization of the sequences is acquired in response to an integrated signal exceeding said threshold at the end of an integration step.

Abstract: The antenna is preferably of the offset type and comprises plural thin and separable parabolic elements jointed into a parabolic reflector, and several substantially rectangular separable panels assembled into a prismatic lattice frame for supporting the reflector. The panels are substantially perpendicular to the lower base of the lattice and have curved upper edges formed in a duplicate mould according to the reflector and separable from the reflector elements. The antenna also comprises a telescopic elevation angle lifting mast and a circular aximuth positioner, both jointed to the frame and dismountable. The dismounted antenna is transportable in the form of standardized packages in the hold of long-distance airliner.

Abstract: The radio system embodying the invention comprises a central station and a passive terminal station. First and second data signals are transmitted between data processing units respectively connected to the central and terminal stations. The terminal station comprises a same low-cost circuit associated with a square two-dimensional antenna for detecting the amplitude of a first incident microwave emitted by the central station thereby recovering the first data signal and deriving, in response to the first microwaves, a microwave modulated in phase by the second data signal by means of a retroreflection of a second incident microwave. This second incident microwave is emitted by the central station to the two-dimensional antenna of the terminal station. The terminal station is of very simple design, is compact and can therefore be included as well as the corresponding data processing unit in a contact-free chip card.

Abstract: A device for the conversion of infrared radiation into another form of radiation of energy greater than that of the infrared radiation comprises a multilayer semiconductor structure (4) comprising at least two layers in which an electron gas and a gas of holes which are regenerated in the course of the use of the device are combined. There is at least one delocalized electron state in the structure, at an energy greater than the energy of the ground state of the electron gas, the difference between these energies being within the infrared range. When the structure is illuminated at a non-normal incidence by radiation (10), the energy of which is equal to this difference, the structure emits a radiation (14) of greater energy, by radiative recombination involving the holes. The device finds suitable application in infrared imaging systems.

Abstract: Method for coding a digital signal, a coder and decoder for implementing this method, a regeneration method and a corresponding regenerator. On each bit time, a detection is made of the possible presence of a binary pattern from any number "n" of binary patterns including at least two bits; the bit time is divided into "n" equal time intervals to which "n" temporal positions are associated; a correspondence is established between each of "n" binary patterns and each of "n" temporal positions; if one of the binary patterns is present, a pulse occupying a temporal position corresponding to the binary pattern is generated and the next detection for the possible presence of a binary pattern is made from the bit following the last bit of the binary pattern whose presence is detected.

Abstract: This device comprises a photoelastic interaction medium between an incident light beam (28) and at least one acoustic or sound wave, as well as means (4, 6) for producing the acoustic or sound wave. The interaction medium is a superlattice (18), which is transparent to the light beam and whose period is close to an integral multiple of half the wavelength of the light beam in the superlattice.Application to the production of acousto-optical deflectors and modulators.

Abstract: A multi-purpose component with integrated optics includes an optical light guide (12) formed on one face of a substrate (10) made of a double refracting material having neutral axes orientated so that one electromagnetic wave extending into the guide (12) is split up into two waves having polarizations perpendicular to each other and along the neutral axes. A power source (18) applies an electric filed perpendicular to the optical light guide (12) and uniformly along the guide (12). Two rectilinear polarizers (20, 22) with polarization directions (d1, d2) parallel to each other are each disposed at one extremity of the guide (12). The component also includes focussing means (24, 26, 28, 30). The component has particular utility for tuneable optical filtering and optical telecommunications.

Abstract: Device able to continuously tune a coherent and rectilinearly polarized light source. It includes an electro-optical device (5) forming a spectral filter with an electrically modulable transfer function, this electro-optical device being provided so as to select a particular longitudinal mode from all the longitudinal modes able to oscillate inside the external cavity for which the source (1) is provided and which is ended by a reflecting device (3) towards the source of the light emitted by this source, and an electro-optical device (4) for varying the optical length of the cavity, this variation device being placed in the cavity and provided so as to continuously move the position of the selected longitudinal mode, each electro-optical device including a compact electro-optical crystal.

Abstract: A filtering cell including a resonant circuit having an inductor and capacitor connected in parallel, the inductor being separated into two identical inductors which are connected in series with a midpoint therebetween. A second capacitor is connected at the midpoint and has a quality factor substantially equal to a quality factor of the first inductor, resulting in attenuation at the resonant frequency. Each of the inductors and capacitors are formed by micro-ribbon technology.

Abstract: Method and device for the geometric characterization of transparent tubes. According to the invention, in order to characterize a transparent tube whose internal and external walls are approximately cylindrical and coaxial, the tube is placed in the air and scanned by an incident luminous beam moved parallel to it within a section plane perpendicular to the axis of the tube. Beams (F0, F1, F2, F3, F4) not deflected by the tube are detected. The detected beams, except for one which passes through the axis of the tube form two pairs. The distance between the two beams of each of these two pairs is determined, and, with the aid of these distances, the internal and external diameters of the tube at the level of the cutting plane are determined. Application for the geometric characterization of tubes for preforms for optical fibers.

Abstract: A process for measuring the dimensions of a spacer consisting in forming in a substrate (1) an array of parallel stripes (2), having a rectangular cross section; forming spacers (7) on the lateral edges (6) of the parallel stripes (2); lighting the array through a monochromatic light beam to supply a diffraction pattern, the envelope of which exhibits a major lobe and secondary lobes; measuring the sum of light intensities of a predetermined number of spots pertaining to the first secondary lobe; and deducting therefrom the width l and angle .theta. of the spacer (7) according to the following formulas:l=k1.times.IL1+k2.theta.=k3.times.

Abstract: An analog/digital converter supplying logic words constituted by P high order bits and Q low order bits, comprises: a divider (2), 2.sup.P high weight comparators (5), 2.sup.Q low weight comparators (11), and a selector (14). The high weight comparators have their second inputs (E21) enabled by the clock signal (H) and their first inputs (E11) enabled by the reverse clock signal (H.sup.*). The low weight comparators have their first inputs (E12) enabled by the reverse clock signal (H.sup.*) and their second inputs (E22) enabled by the clock signal (H).

Abstract: A sound signal coding method and installation are disclosed, which method, usable particularly for transmitting or storing high quality audio signals in digital form, involves chopping the sound signal into blocks of samples and subjecting the samples of each block to time-frequency transform coding whose coefficients are transmitted in digital form, the reverse operations taking place at reception. At least the most significant coefficients of the transform of each block are subjected to predictive and adaptive coding using the stationary state of the signal over a duration greater than that of a block.

Abstract: A non-resonating laser diode optical amplifier comprises a strip of optically active material forming an amplifying optical guide, covered with a confinement sheath and defined by antireflection coating layers. The strip has end portions whose thickness is lesser than that of a central portion and is selected to give a low value to the difference between the wavelengths corresponding to the reflectivity minima for the two inherent polarization states. The end portions are connected to the central portion by transition sections having a progressively increasing thickness.