Abstract: A feedback circuit for controlling the phase of a local oscillator provided with frequency adjusting means and delivering a local carrier wave for demodulating a data signal transmitted by single side band amplitude modulation, the said feedback circuit comprising at least one sign multiplier (21) producing the product of the sign of the local demodulation carrier shifted by a phase difference of .pi./4 multiplied by the sign of the data signal to be demodulated, followed by a sign coincidence auto-correlator (22) which controls the said frequency adjusting means and correlates two versions of the signal delivered by the sign multiplier (21), one of the two versions being delayed relative to the other by an odd multiple of one fourth of the period of the carrier used for the amplitude modulation on transmission.

Abstract: There is a need to recover the clock rate from a received and demodulated binary data signal in order to properly decode the received data. Unfortunately some linear modulation systems used for transmission have the effect of ensuring that there is substantially no frequency component in the received signal at the desired clock rate. Non-linear processing of the received signal (e.g. by a rectifier circuit) is therefore necessary to recover the clock. A simple rectifier circuit system is sensitive to the phase difference between the transmitter and receiver carrier waves. The present recovery circuit (10) requires a quadrature demodulator (9) to provide in-phase and quadrature versions x.sub.1 (t) and x.sub.2 (t) of the received demodulated data signal. Two parallel chains of rectifier circuit (30,31), on/off limiter (32,33), multiplier (34,35) and low pass filter (36,37) act separately on the said versions.

Abstract: The present invention comes within the field of synchronous digital transmission. It relates to the recovering the carrier (which may be suppressed carrier) of an amplitude modulated synchronous digital signal. It provides a circuit which includes an oscillator (41) of adjustable frequency and phase to generate a local carrier, a demodulation circuit whose input(s) receives the local carrier (possibly phase shifted by .+-..PSI. (42,44,46,47) and the amplitude modulated synchronous digital signal e(t) and control means (48,49) which control the phase and the frequency of the oscillator from the signals delivered by the demodulation circuit and which comprise at least one sign coincidence autocorrelator. It advantageously applies to demodulating amplitude modulated single side band bipolar coded synchronous digital signals.

Abstract: The present invention comes within the field of synchronous digital transmission. It provides an automatic variable equalization network (1) equipped with phase-locking means, in which a sign coincidence autocorrelator (30) correlates the polarities of two versions of the equalized signal delayed in relation to each other by .tau., an integer multiple of the unit time interval of the transmission. It is used advantageously for equalizing synchronous digital transmission channels in switched telephone or telegraph networks.

Abstract: A device for regenerating telegraphic signals without bias distortion and noise, using, essentially, a peak limiter fed with direct current voltage from the input signal and a comparator comparing the output signal leaving the peak limiter with a decision potential. The device is used in a telegraphic connection, at the end of a subscriber cable coming from a telephone terminal.