Abstract: In order to deliver an angle-modulated output signal as a function of digital information, the frequency synthesizer delivers an output frequency F.sub.S =(N+k)F.sub.R, where N is the integral part of a number N+k and F.sub.R is a reference frequency. Provision is made for a variable oscillator, an oscillator control loop comprising in series a variable divider having a preselected divisor N, a phase comparator for receiving the reference frequency and a summing device. The synthesizer further comprises a phase accumulator for performing, at the frequency F.sub.R, modulo-M summation of a number G=k(M) applied to its input. The sum and carry outputs of the accumulator are coupled respectively to the summing device in order to deliver a signal for compensating the signal delivered by the phase comparator and to the divider for delivering a control signal to select the divisor N+1.

Abstract: The process uses a set of data characteristic of the speech signal, supplied by processing circuits: measurements of the time intervals between zero crossovers and measurements of the energy in the half-waves of this signal. The test procedure implemented by a microprocessor selects the half-waves whose energies exceed thresholds characterizing pitch period beginnings. These thresholds are predetermined for the first two successive sums selected, then depend on the energy values of the preceding half-waves selected differently according as to whether the voiced character of the signal is acquired or not. Complementary tests are used for minimizing detection errors.

Abstract: In a multiplexed filtering device the first and second input signals are respectively sampled to give a third signal and sampled and delayed to give a fourth signal. An adder whose output is connected to the control electrode of a charge transfer device of a hybrid filter, adds alternately the third signal to a sampled signal corresponding to the third signal and coming from the recursive part of the hybrid filter and the fourth signal to a sampled signal corresponding to the fourth signal and coming from the recursive part of the hybrid filter. The output signals of the non-recursive part of the hybrid filter are summed by a reading amplifier, the output of which constitutes the output of the hybrid filter; after which they are demultiplexed and delayed for the restoration of the first input signal and only demultiplexed for the restoration of the second input signal.