Abstract: In order to restore a clock signal which has been used for coding signals transmitted on a transmission channel, the transition instants of these signals are precisely detected by analyzing a series of samples taken from the signals during at least one fraction of the clock period. A device first determines the deviations between the respective amplitudes of the various samples that have been taken. Comparison of the deviation configuration obtained with standard configurations that have been determined previously makes it possible to estimate the position of the time window where the sampling was achieved in relation to the analyzed period fraction and therefore to decide whether this window is correctly centered. If it is not, a local clock is phase shifted so as to have the time window resynchronized.

Abstract: A device for simplifying transmission of analog signals received from sensors to a remote station in accordance with the invention includes at least one local electronic module including in combination a modulator for oversampling each analog signal and converting each oversampled analog signal into lower resolution digital words and a transmitter for transmitting the lower resolution words as a bit stream on at least one first transmission channel; at least one synchronization element producing a clock signal allowing synchronization of each modulator with the remote station; and at least one reception module in the remote station including a receiver for receiving the transmitted lower resolution words as a bit stream and a digital filter, coupled to the receiver, for converting each received bit stream received into digital words of a higher resolution (typically 16 or 24 bit words. The invention is useful for transmission of seismic data.

Abstract: Analog signals picked up by sensors are oversampled and converted locally for example into streams of 1-bit digital words and, without any previous formatting are transmitted on transmission channels to a central station. The central station includes a storage and a combining circuit for combining and weighting directly these 1-bit words, as well as a filter for reconstituting, from the combinations, high-resolution digital words.A preferred application is combining of acoustic or seismic signals.

Abstract: Measurement of the successive levels of a received signal is achieved by combining together the elements of groups of digitized samples (E1 to Em) which are taken from the signal during successive sampling windows (W) positioned by a local clock (H) kept thoroughly synchronous with the signal. The combination consists of a weighted average so as to take account of the transmission conditions: passband of the channel, required flow rate, background noise, etc, likely to distort the signals transmitted and therefore to lead to errors in the measurement of the actual levels thereof. Such weighting is achieved by using the set of digital samples (E1 to Em) corresponding to a single group, for addressing a memory (10) in which the values to be selected for each one of the digital words have been previously stored.

Abstract: A device is provided for locking the frequency and phase of a signal to that of a signal imposed, of the phase locked type. It comprises a modulator mixing a signal whose frequency is proportional to that of a reference signal coming from an oscillator. The low frequency component of the combined signal (isolated by an integrator) is permanently applied to the oscillator to an input with relatively low sensitivity, for the fine corrections, and to a high speed loop comprising a storage element and an amplifier, through a switch controlled by a window comparator. The high speed loop is connected to a higher sensitivity input. The high speed loop only acts during the setting period, for bringing the control voltage of the oscillator back to close to the optimum voltage, the optimization being provided by the permanent loop.