Telecommunications Radioelectriques Et Telephoniques T.r.t.

Alcatel

Telecommunications Radioelectriques Et Telephoniques

Societe Dite Alcatel N.v.

Jean Lassaux

Michel Levy

Jean Adrien Guezou

Henry Clement

Thierry Stephan

Christian Dagorn

A subscriber card includes a controller for concentrating Internet frames so as not to occupy a telephone circuit for each call to an Internet service provider. The subscriber card is connected to a switching matrix that facilitates transmission of the concentrated Internet frames to a data transmission network. The subscriber card handles multiple subscriber inputs and statistically multiplexes data from the multiple subscriber inputs in order to increase throughput.

Subscriber card, a subscriber unit, and an exchange for concentrating internet frames

Subscriber card, subscriber connecting unit and relay centre for concentrating internet frames

A device for connecting a station to a local area network comprising at least one ring includes switching arrangements associated with circuits for regenerating a signal in order to bypass a station when it is out of service and compensate the attenuation and phase jitter caused by the upstream ring segment. This device enables any number of stations to be taken out of service without seriously degrading operation of a ring. The device is usable in local area networks comprising one or more high-speed (125 Mbauds) rings.

Device for connecting a station to a local area network comprising at

The apparatus for detecting and discriminating phase jumps in a periodic signal comprises, arranged in cascade between an input terminal (1) and an output terminal (2), a frequency converter (3) transforming the frequency spectrum of the input signal e(t) containing a line at the frequency f.sub.e in a continuous band spectrum whose frequency is centered around f.sub.e, an interrupter (4), a resonator (5) having a resonant frequency f.sub.0 near f.sub.e and a phasemeter (6) having detection and discrimination means. The ensemble of these elements (3-6) is controlled by a sequencer (7) which, at each period .alpha. such that .alpha.=t.sub.1 +t.sub.2, allows the phase detection and the discrimination of each phase jump of a predetermined value .DELTA..phi..sub.e which may be contained in the input signal at the frequency f.sub.e.

Apparatus for detecting and discriminating phase jumps in a periodic

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.sub.AV is below a threshold a, the clipping threshold varying in accordance with an increasing function of the level N.sub.AV.

Echo canceller and center clipper control arrangement

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.

Equipment for locating a signal reflection point in a transmission line

A digital echo canceller is arranged in a digital telephone circuit for PCM-signals in accordance with a pseudo-logarithmic encoding law, for example the A-law of the CCITT, in the proximity of a subscriber line interface circuit having a codec in order to cancel in the near-end speech signals S supplied by the codec to the send path the echo effect Y of the far-end speech signals X conveyed to the codec by the receive path. The echo canceller has circulating shift registers for the signals X and the coefficients C, digital correlation calculation means for obtaining the coefficients C, digital convolution calculation means for obtaining an echo cancellation signal y and digital subtraction calculation means for obtaining near-end speech signals R in which the echo effect Y has been substantially cancelled. Each of the digital correlation, convolution and subtraction calculation means incorporates only one pseudo-logarithmic-to-linear code converter, and furthermore the digital subtraction calculation means incorporates only one linear-to-pseudo-logarithmic code converter.

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Lannion, France

Jean Lassaux