Abstract: A device for transmitting and decoding audio-visual streams arranged in accordance with standard ISO/IEC 11172 is provided. The device (DEC) comprises: interfaces (CSC, IA, CIS) for connection to a local storage device (MEL) or to a telecommunications network (2, 3), for receiving streams from remote sources or send streams to remote receivers; demultiplexing and synchronisation means (DES) for splitting the audio-visual streams into constituent audio, video and private data streams and extracting synchronisation information from the streams, and means (DA, DV, UA, UV) for decoding audio and video streams and present audio and video signals in analog form at the output. A controller (CNT) is to control and supervise demultiplexing and decoding operations.

Abstract: A decoder for audio signals belonging to audio-visual streams coded in accordance with standard ISO/IEC 11172 is provided. The decoder has a presentation unit (UP) which is controlled by a first and a second clock signal, depending on the desired sampling rate, and is associated to device for (SAV) managing audio-video synchronization. The latter device starts the presentation of output data by comparing a first timing signal (SCR), representative of a system clock signal, and a second timing signal (PTS), representative of a correct instant of data presentation, independently generate the two clock signals (CLK24, CLK22) and corrects the signal corresponding to the desired sampling rate with the use of a feedback circuit which includes a digital filter (FD).

Abstract: To determine the polymerization profile of a layer of polymeric material, particular a coating of an optical waveguide, a source sends a light radiation towards the layer under test at different angles of incidence, and both the portion of radiation reflected by the layer and the portion transmitted by the layer are converted into electrical signals. The electrical signals are supplied to devices for measuring their intensity, and a processing system processes the intensity values to obtain a value of the refractive index at a different depth inside the layer and to obtain the degree of polymerization at each depth by comparison with the values of the refractive index of a precursor of the polymer and of the fully polymerized material.

Abstract: The peripheral unit for multi-videoconferencing permits multi-videoconferencing while fully exploiting the characteristics of a telecommunications satellite, and can also provide the service to users not connected to the ground network. In particular, the system can connect several remote rooms through a satellite network, interfaceable with a ground control center, to provide an overall mixed ground-satellite network able to simultaneously serve both permanent and temporary users. The peripheral unit is connected on one side to the transceiving station for the satellite link and on the other to the encoder and decoder of video and audio signals, which are generated locally or received from a remote station and organized according to a protocol provided with time-slot frames and superframes.

Abstract: A method and a device for speech signal digital coding are provided where at each frame there is carried out a long-term analysis for estimating pitch period d and a long- term prediction coefficient b and gain G, and an a-priori classification of the signal as active/inactive and, for active signal, as voiced/unvoiced. Period estimation circuits (LT1) compute such period on the basis of a suitably weighted covariance function, and classification circuits (RV) distinguish voiced signals from unvoiced signals by comparing long-term prediction coefficient and gain with frame-by-frame variable thresholds.

Abstract: An optimum excitation signal for each subframe is determined in a speech coder based on analysis-by-synthesis techniques and operating on frames of samples divided into a number of subframes. The excitation signal includes a shape contribution (innovation) and an amplitude contribution (gain) which are quantized separately. A circuit (IT) for gain quantization includes means (QU) for determining a gain index for each subframe; a comparison logic network (CFR) for detecting the maximum value taken by the gain index in the frame; and means for computing a normalized index for each subframe as a difference between the maximum index and the gain index relevant to that subframe. The coded signal includes the coded values of the maximum index and of the normalized indexes as information on the gain relevant to a frame.

Abstract: The set of possible excitation signals is subdivided into a plurality of subsets, the first of which provides the contribution to the coded signal necessary to set up a transmission at a minimum rate guaranteed by the network, while the others supply a contribution which, when added to that of the first subset, causes a rate increase by successive steps. At the receiving side, a decoded signal is generated by using the excitation contribution of the first subset alone if the coded signals are received at the minimum rate, while for rates higher than the minimum rate the contributions of the subsets which have allowed such rate increase are also used.

Abstract: The set of possible excitation signals is subdivided into a plurality of subsets, the first of which provides the contribution to the coded signal necessary to set up a transmission at a minimum rate guaranteed by the network, while the others supply a contribution which, when added to that of the first subset, causes a rate increase by successive steps. At the receiving side, a decoded signal is generated by using the excitation contribution of the first subset alone if the coded signals are received at the minimum rate, while for rates higher than the minimum rate the contributions of the subsets which have allowed such rate increase are also used.

Abstract: A multimedia protocol interface for 64K Kbit/s data flow, organized accorg to the frame structure specified in CCITT Recommendation H221 and transmitted and received according to the standard 64 kbit/s protocol or 256 kbit/s 10 M protocol, adapted to operate autonomously or aided by an external microprocessor and has a receiver, a transmitter, a control block and circuitry for the local test of the operation of the interface itself. The external microprocessor can read both the received data and the information relevant to the receiver conditions, and can also send data to be transmitted or can read information relevant to the transmitter conditions. The receiver receives the data and clock and synchronism signals and emits at the output the received data, associated with timing signals useful for the external devices connected to the interface for data recovery. Analogously, the transmitter emits the data, receives clock an synchronism signals and supplies data and timings to the external devices.

Abstract: Silica intended to form the core of an optical-fibre preform is deposited as an unvitrified soot inside a reaction tube, where a non-aqueous solution of dopant precursor(s) is then introduced without removing the tube from the lathe. The precursor(s) of the dopant(s) are dissolved in an anhydrous organic solvent. The solution containing the dopant precursor(s) is introduced into the reaction tube without removing the tube from the lathe so that the solution covers the whole surface of the deposited soot layer and impregnation of the deposited soot layer occurs.

Abstract: Detection system for cathodoluminescence analysis apparatus, wherein a screen is placed between the sample to be analyzed and the detector to intercept the electrons backscattered by the sample towards the detector. The screen is a plate of a glass which is transparent in a wide spectral interval, has a rather high conductivity, and does not present cathodoluminescence effects.

Abstract: The instrument measures directly the phase jitter of analog signals emitted n the line by the device under test, even when clock information is not available and when particular specifications and limitations do not allow the use of analog instruments. It uses a circuit which generates a square-wave clock signal with the same phase and frequency characteristics as the signal to be measured, so as a phase comparison with a reference signal can be made. Error signal obtained is filtered, measured and displayed.

Abstract: The echo canceller for bidirectional digital transmission systems cancels the echo queues of a desired number N of digital symbols, transmitted on the line in the last N signalling periods. It consists of a part which effects very simply the summation of the last N transmitted symbols, so as to ease the system implementation by an integrated circuit, and of a part which computes the estimated sample of the echo-channel pulse response. The results of the two parts are multiplied by one another and the estimated echo signal is obtained.