Abstract: For processing data signals representative of pixels, each of the pictures s scanned, column per column in successive horizontal bands each having a height equal to an entire fraction of the height of the picture, whereby a representation of the picture as pixels distributed in rows and columns is obtained, each band having a common predetermined number of rows. The picture is fractionated into mutually adjacent blocks of pixels each having M pixels in each of N mutually adjacent columns, M and N being predetermined integers and M being a simple multiple of the number of pixels in one column of a band and N being a whole fraction of the number of colums per image.

Abstract: A holographic method of the type implementing a conoscopic system including a birefrigent crystal inserted between two polarizers and a photosensitive element, wherein the method includes a step consisting in inserting one-dimensional optical means on the path of the light rays such that the conoscopic system only collects light that is parallel or quasi-parallel to a plane including the axis of the conoscopic system. The invention also provides apparatus for implementing the method.

Abstract: A holographic apparatus of the type comprising a conoscopic system including a birefringent crystal inserted between two polarizers, wherein the apparatus also includes an aperture angle limiter inserted on the path of the light rays and wherein one of the birefringent crystal and the aperture angle limiter is disposed off the optical axis of the apparatus.

Abstract: A spectrum analyzer for a variable amplitude and frequency electric signal includes an optical modulator responsive to the signal that derives a first optical wave having intensity and frequency components corresponding to the signal amplitude and frequency components. An optical analyzer responds to the first optical wave to derive a second optical wave having intensity variations at frequency components corresponding to the amplitude of the electric signal at the frequencies in the spectrum of the signal. The optical analyzer includes a tunable optical cavity responsive to the first optical wave to derive the second optical wave.

Abstract: An information encryption method particularly intended for a communication system in which bidirectional multiplexed communications of the point-to-multipoint type are derived between a switching exchange and plural terminal stations. The switching exchange transmits first multiplexed words respectively destined for the terminal stations. The terminal stations supply second words which are multiplexed and transmitted towards the switching exchange. In the switching exchange, informations concerning transmission errors detected in the second words are derived and transmitted towards the terminal stations, and the first words are encrypted as a function of second words previously received free of transmission error in the switching exchange. In each of the terminal stations, the informations concerning the transmission errors are detected, and the second words transmitted from the terminal station and received free of transmission error by the switching exchange are memorized.

Abstract: The radio system embodying the invention comprises a central station and a terminal stations or passive end. Data signals are transmitted between data processing units which are respectively connected to the central and terminal stations. The radio system is essentially characterized in that the terminal station comprises a square two-dimensional antenna and a microwave switcher so as to phase modulate, by means of a data signal, a microwave transmitted from the terminal station to the central station. This phase modulated microwave is produced from an incident microwave transmitted by the central station and issued to the terminal station by the square two-dimensional antenna. The design of the terminal station is very simple and compact and can be included, as well as the corresponding data processing unit, in a contact-free chip card.

Abstract: An echo cancelling device for use between a line receiving an incoming signal and a line transmitting an outgoing signal, for cancelling out echo, comprising a plurality of processing channels connected in parallel relation and assigned to successive mutually adjacent sub-bands of the spectral band of the outgoing signal, each channel having: a first analysis band-pass filter receiving the echo-affected signal to be transmitted, whose output is connected to the additive input of a subtractor; a second analysis band-pass filter, identical to the first filter, receiving the incoming signal and feeding an adaptive filter delivering an estimated echo value in the sub-band to the subtractive input of the subtractor; and a synthesis filter, symmetrical with the analysis filters and whose output feeds the transmission line.

Abstract: For filtering a bi-dimensional image signal in the form of data representing pixels obtained by column per column scanning of bands each having a height equal to a fraction of the height of the image, the transform of each pixel is computed in turn. For that, a convolution product using MxN coefficients is carried out on the pixels of a zone of an image, each column of each M pixels. The image is fractionated into mutually adjacent blocks each representing N columns of M pixels and the transforms of all pixels of a same block are simultaneously computed in MxN cycles by: parallel computation, during a same cycle, of all partial convolution products of only one of the filtering coefficients and of those pixels which provide a partial product which intervenes in the computation of the transforms of all pixels of the block, within a "window" of the picture which contains the block. The cycle is repeated for each coefficient in turn. All partial products obtained during the successive cycles are summed.

Abstract: A differential encoder for speech encoding, typically in a 16 kHz wide band, has a self adaptive predictive filter, comprising a comparator receiving, on an additive input, successive samples of a signal to be encoded and, on a subtractive input, an estimated signal delivered by a prediction loop which receives the error signal from the output of the comparator, the prediction loop comprising a self-adaptive predictive filter, a gain control circuit and a multiplier which receives the outputs of the predictive filter and of the gain control circuit and whose output is connected to the subtractive input.

Abstract: A first switching network embodying the invention is a subscriber installation having a chain structure. In the network, the switching is distributed over a plurality of switches each connecting a terminal to the network. A second embodiment is a business network having a star-chain structure and comprising a plurality of sub-networks of chain type. The sub-networks are star connected to central switches which operate in a load sharing mode. According to the method embodying the invention, the terminals connected to the network assume themselves the responsibility for determining communication routes through the network. During a communication set-up phase, caller and callee terminals transmit call packets which are disseminated to all terminals in order to measure two so-called "distances" respectively between the caller and the callee and between the callee and the caller. These distances are after included in data packets for routing said packets.

Abstract: A device for real time computing of a sum of terms having the form .SIGMAiT).qe((n-i)T) is suitable for use in an echo canceller for a data transmission system using code 2B 1Q. The device first transforms each of the successive estimated values of qe into transformed values qde which are powers of two, by adding or subtracting 1. The successive elementary products each obtained by a shift of h by an amount selected in response to the respective value of qde. The elementary products are summed in a register.