Abstract: In a signal analysing and synthesizing filter bank system, the analysing bank receives a signal sampled at the rate f.sub.e and produces N contiguous subbank signals sampled at the rate f.sub.e /N. From the subband signals the synthesizing bank must recover the incoming signal. These filter banks are formed by modulation of a prototype filter by sinusoidal signals which, for subband k (O.ltoreq.k.ltoreq.N=1), have a frequency (2k30 1)f.sub.e /(4N) and respective phases +(2k+1).pi./4 and -(2k+1).pi./4 for the analysing and synthesizing banks. These signals are furthermore delayed by a time delay (N.sub.c -1)/2f.sub.e), where N.sub.c is the number of coefficients of the prototype filter.

Abstract: A data processor for executing a program of instructions stored in a program memory controlled by a program counter. To execute a loop control instruction, calling for repeated execution N times of a sequence of "i" instructions, the processor includes a loop circuit having an instruction counter which counts execution of the instructions in the loop sequence and produces an end-of-sequence signal upon each completion of the loop, a register which refreshes the program counter with the address of the first instruction in the loop in response to each end-of-sequence signal, and a loop counter which counts the number of completions of the loop and delivers a signal indicating the end of the loop portion of the entire program and enabling the program counter to continue on with the rest of the program. The delay in loop execution permits initializing of registers in the data processor so as to permit pipeline execution of the loop instruction.

Abstract: Echo canceler associated with a modem utilizing amplitude and phase modulation of a carrier, the echo canceler comprising adaptive filters (16-1) to (16-p) producing signals which are combined in an adder (15) for forming a synthetic echo signal .epsilon. (n). The coefficients of these filters are adjusted to minimize the mean square value of the residual echo signal e(n)=.epsilon.(n)-.epsilon.(n), where .epsilon. (n) is the echo received. The echo canceler comprises a code conversion circuit (17) which receives a signal D(n) characterizing in each modulation interval the amplitude and phase state of the carrier to be transmitted and which produces distinct configurations of several veral numbers of values +1, -1 or 0, said distinct configurations corresponding to the distinct possible states of the carrier to be transmitted such that elementary signals D.sub.1 (n) to D.sub.p (n) are formed which are mutually independent in the mean and which are applied to the filters (16-1) to (16-p).

Abstract: Apparatus for controlling the transmission power of a transmitting station over a digital radio communication channel, based on information relating to the level of the signal received at a receiving station and information relating to the quality of such received signal relative to a predetermined error rate. The signal level information and signal quality information is derived by respective threshold measurement devices in the receiving station, and is transmitted back to the transmitting station over a return channel. The transmitting station comprises means for effecting combined processing of such information to derive a control signal which controls means for increasing or decreasing the transmitting power over a dynamic adjustment range. In a first part of such dynamic range such control is based only on the information relating to received signal level, and over a second part of such range such control is additionally based on the quality of the received signal.

Abstract: A processor for carrying out a calculation mode from a selected plurality of different modes. The processor includes a clock pulse generator which generates clock pulses in an order for processing subsequent data. A mode circuit is included for detecting a mode declaration instruction. The mode declaration instruction is decoded to select a different clock pulse cycle for each different mode selected. Mode control signals and the selected clock pulse cycle are applied to a control code and borrow management circuit to enable the arithmetic and logic unit to carry out one or more operations of the mode control signals.

Abstract: An arrangement ensuring the change-over of two channels through which the same digital information is conveyed with automatic data alignment over a .+-.3.5 bit range comprises for each channel an array of buffer stores operating at a write rate H.sub.i /N.sub.i (where i=1, 2), an oscillator operating at a rate H which provides reading of the buffer stores at the rate H/N and being synchronized in phase-opposition with one or the other of the write rates, and a logic comparator controlling the write rates H.sub.i /N.sub.i, the routing of the write rates to the input of the oscillator, as well as a change-over switch for the data.In the buffer store of the channel assumed to be the one whose quality degrades, the data are converted into N parallel streams at the rate H.sub.2 /N and are read at the rate H/N of the oscillator. In the other channel, the write rate of the buffer store is forced to the rate H.sub.

Abstract: A sight comprises an image carrier (D) presenting an exit aperture (P3) and forming, from an observed image (I), an intermediate image (I') at the focus (F) of an ocular comprised of a spherical mirror (M) with the same optical axis (XX') as that of the image carrier (D), with a holographic beam deflection element (H) being placed at the focus (F) of the spherical mirror (M). In accordance with the invention, the intermediate image (I') is formed on the focal surface (S) of the ocular, and the holographic beam deflection element (H) is disposed on a support resting on the focal surface (S) and, in association with the spherical mirror (M), conjugates stigmatically the exit aperture (P3) of the image carrier (D) with the exit aperture (P1) of the sight.

Abstract: A system for transmitting information between at least two stations the information originating from free or engaged channels in a multiplex frame, each station comprising at least one transmitting circuit and one receiving circuit powered from a power supply, and means for detecting the free and engaged channels to provide a procedure for establishing a multiplex formed by an elementary frame in which the engaged channels are grouped side-by-side in the elementary frame and means for reducing the power consumption of the transmitting and receiving circuits.

Abstract: An optical and mechanical scanner including a device for scanning a field of vision to detect and recognize with high resolution distant objects in the field of vision. Scanning is accomplished in two directions including a direction x for line scanning and a direction y for raster or image scanning. One embodiment of the scanning device includes, in order along the direction of a path of a mean incident beam from the field of vision, an objective, a raster scanning mirror for scanning in the y direction, a field mirror which delimits the field of the objective in the x direction, a rotating drum and an image transport system for line scanning in the x direction, the field mirror deflecting the beams towards the drum, and a detector sensitive to the radiation contained in the beams, the scanning device ensuring convergence of the beams at the detector.

Abstract: A telephone switching system is formed on the basis of a switching network intended to switch message information by interconnecting input circuits provided with programmed-logic units. Among these programmed-logic units are incorporated for the purpose of transmitting control information connecting circuits formed by Pierce loops in which control circuits of the switching network are inserted.

Abstract: This arrangement is intended to control the operation of the coefficients adjusting circuit (12) of an echo canceller and of the operation of a center clipper (15) inserted in the send path (7) of a four-wire circuit at the output of the subtractor (13) of the echo canceller for suppressing there, when it is set to its active state, the signals whose amplitude is lower than or equal to a clipping threshold. The control arrangement operates on the basis of the signal in the receive path (2) of the four-wire circuit, the level N.sub.REC of this signal and the levels N.sub.AV and N.sub.AP of the signals before and after the subtractor (13). It comprises a controller (21) for comparing the level N.sub.AV to two fixed thresholds N.sub.AV0, N.sub.AV1 and for comparing the ratio N.sub.AP /N.sub.AV to a threshold a which is capable of varying as a function of N.sub.AV, the center clipper being only set to its active state when the level N.sub.AV is comprised between N.sub.AV0 and N.sub.AV1 and the ratio N.sub.AP /N.

Abstract: The invention relates to a device for optically scanning a field of vision divided into different regions and for displaying the field, scanning being done in two perpendicular directions, i.e. "line" scanning in a direction x and "raster" or "image" scanning in a direction y, the device scanning along beams coming from different regions of the field and causing the beams to converge on to an element sensitive to the radiation in the beams, the present invention being concerned particularly with the line-scanning means, which is designed so that the device can operate with smaller apertures without affecting its resolution. The line-scanning system comprises a rotating drum having reflecting surfaces but the detector image is conveyed outside the drum axis.

Abstract: In an equipment for locating a reflection point in a transmission line a recording is obtained of the impulse response of the path of the echo produced by a transmission signal based on a reference signal x(n) constituted by binary sequences of duration NT which comprise only one bit of non-zero value. At the reception end, the equipment comprises a memory for storing N coefficients Ci which are read cyclically with a view to being modified by successive iterations, each coefficient being modified once per read cycle by the term .alpha..Sgn[e(n)], where Sgn[e(n)] is the sign of the difference between the signal received and the coefficient read at a moment NT and .alpha. is a constant less than 1. The coefficients modified and written into the memory form the values of the desired impulse response.

Abstract: The filter coefficients of an echo cancelling arrangement having a near echo canceller and a distant echo canceller are initialized in accordance with a method and apparatus wherein the following steps are performed:transmission of at least two training sequences each comprising a pair of complementary S and C sequences having autocorrelation functions such that, if added, their sidelobes cancel, each S and C sequence being followed by a variable time interval .DELTA., determined as a function of the measured distant echo delay .tau.

Abstract: A method of reducing the convergence time of an echo canceller including a transversal filter having N coefficients comprises at least the following steps:transmission of a training data signal D(n) constituted by data transmitted at instants nT, T being the data interval, and being periodically reproduced after a duration LT at least equal to NT and having the property: ##EQU1## where d and d.sup.x are the value of the data signal D(n) and its complex conjugate value, respectively;calculation of the coefficients of the transversal filter carried out after the instant of appearance of the echo signal produced in response to said training signal in accordance with the expression: ##EQU2## where C and C.sub.o are the vectors of the N coefficients of the transversal filter at the beginning and at the end of the period of calculating the coefficients, respectively,e(n) is the difference signal,D.sup.x (n) is the vector of the complex conjugate values of the N data stored in the transversal filter, and.sigma..sup.

Abstract: D.C.-fed ringing signal generator for a group of subscriber lines comprises a cascade arrangement of a digital signal generator controllable by a control signal to produce a signal corresponding either to the ringing signal or to a signal having zero value,a digital-to-analog converter,a capacitively-coupled class-A amplifier, anda direct-coupled class-B symmetrical power amplifier to produce the output signal of the ringing signal generator.

Abstract: A self-adaptive equalizer for use in a data modem for correcting in the baseband a received data signal. The equalizer comprises a difference circuit for determining the difference between a received signal and a correction signal formed at a sampling frequency by a transversal filter having adjustable coefficients, and which produces a corrected signal which is applied to a decision circuit which recovers the data signal. The output of the decision circuit is applied to the transversal filter, the coefficients of which are adjusted so as to minimize the mean-square value of an error signal. The error signal at each actual sampling instant is formed by deriving the algebraic difference between the value of the corrected signal at that sampling instant and the value thereof at a previous sampling instant, the latter value being first multiplied by the ratio between the value of the recovered data signal at the actual sampling instant and the value thereof at the previous sampling instant.

Abstract: Method and apparatus for measuring the delay of the distant echo in an echo ancelling arrangement comprising a near echo canceller, a delay line and a distant echo canceller using the steps oftransmitting, by modulation of a carrier, a data sequence having a periodic autocorrelation function with sidelobes of negative or zero value, this sequence having a duration at least equal to the maximum value of the delay to be measured and a number of elements determined by the accuracy desired for measurement of the delay;calculating the correlation function between the data of a next transmitted sequence and the data formed by demodulating the received signal and storing calculated samples of the correlation function in a memory; and determining, among the samples stored, the sample corresponding to the maximum of the correlation function and the rank of that sample.

Abstract: An FSK modem transmission circuit which includes a modulator adapted to sctably produce pairs of low and high frequency carrier waves in any combination of up to five frequencies specified in international and U.S. standards. The modulator circuit includes a regenerative feedback loop which generates a triangular carrier wave at a frequency determined by the resistance of a resistor network having five different settings selected by switches therein controlled by the data signal and by logic control signals. The transmission circuit also includes a filter which modifies the waveform of the transmitted carrier wave to suppress odd harmonics thereof, thereby isolating the carrier wave from the modem receiver circuit which is coupled to the transmission circuit by a hybrid coupler.

Abstract: Method and apparatus for reducing the convergence time of an echo canceller including a transversal filter having N adjustable complex coefficients comprises the following steps:transmitting a complex training signal constituted by data d(n) transmitted at instants nT, where T is the data interval, having a period LT at least equal to NT and having the following two properties: ##EQU1## for every integer i such that 1.ltoreq.i.ltoreq.N-1, and ##EQU2## for every integer i such that 0.ltoreq.i.ltoreq.N-1; after the transmission of N data, calculating the coefficients C of the transversal filter from the sequence formed by the next L data transmitted, in accordance with the expression: ##EQU3## where C.sub.o represents the N initial coefficients,e.sub.R (n) is the difference signal between the received signal and the real output signal of the transversal filter,D.sup.* (n) represents the complex conjugate value of the last N data entering the transversal filter, and.sigma..sup.