Abstract: A digital filter providing output samples at a rate B while input samples are being provided at a rate A. The filter impulse response h(t) is sampled at a rate P=a.A=b.B, with P being the lowest common multiple to A and B, to derive Np filter coefficients therefrom. The coefficients are arranged into "a" sets of Np/a coefficients and stored. Output samples are then computed by feeding input samples Sn at incoming rate while permutating the sets of coefficients and generating output samples at the output rate.

Abstract: Modem receiving from/transmitting to a DTE data bits at a rate DR and adapted for operating at a modulation rate MR in an environment operating at a basic rate BR. In the receiving way, it comprises a first means for converting a number X of samples received at a frequency FS into a number X times MR/BR of samples before processing these samples by the signal processor whereby the processing results in DR/BR words of DR/MR bits, and second means for converting the DR/BR words into DR/MR words of DR/BR bits to be transmitted to the DTE. For the transmitting way the first and second converting means, are the same means but run in the reverse order. The result is that such an adapted modem behaves as a modem operating at a modulation rate MR on a periodic process interval of DR/(BR times MR) seconds.

Abstract: Echo cancelling device for cancelling echoes affecting the incoming signal received over a two-wire telephone line, comprising near echo canceller 20, far echo canceller 22 and an adder 26 providing the estimated echo signal. A circuit path including a digital-to-analog converter 48 for converting the digital estimated echo signal into analog form and a subtracter 52 for subtracting the resulting analog signal from the analog incoming signal, is separated from a circuit path including an analog-to-digital converter 42 for converting the analog incoming signal into digital form and a subtracter 44 for subtracting the digital estimated echo signal from the resulting digital incoming signal thereby providing a digital signal used as a control signal for adjusting the echo cancellers 20 and 22.

Abstract: Echo cancelling above for providing an echo-free incoming data signal with a phase-roll tracking device comprising phase rotating means (58) for rotating the phase of the generated echo signal by a value X which is the estimated phase-roll value, thereby providing a complex phase-roll corrected echo signal a multiplier (124) for multiplying the error signal; between the incoming signal and the real component (112) of the phase-roll corrected echo signal by the imaginary component (120) of the same signal, thereby providing a value Y function of the variation of the phase-roll; a phase-roll variation estimator (128) providing an estimation Z of the phase-roll variation in half duplex mode or in full duplex mode, in response to value Y; and a phase filter (126) providing the estimated phase-roll value X in response to the estimation Z.

Abstract: A DTE can control the modems attached thereto by transmitting command messages over the data path and analyzing report messages supplied by the modems in return. Each command message is identified by a specific header. A command message intended for a remote modem (34) is intercepted by the local modem (30) and reformatted so as to obtain a supervisory message that is then transmitted at the rate of one bit per baud. A command message intended for a remote multichannel modem (48) is transmitted either by a supervisory message or in the data mode of operation.