Abstract: The invention comprises several groups of local units (BA) suited for the acquisition, the processing and the transmission of data collected in the field by seismic receivers, each of these groups being controlled by a local station (LS) equipped to fulfill extensive functions including collection of the seismic data of the various units, management of testing and initialization operations on radio channels and on the field equipment such as seismic receivers (R), electronics in each unit RTU, monitoring of the progress of seismic operations, and reporting on results and possible anomalies. The seismic set comprises several groups (GR) of receivers, with associated local units and a local station, which are placed under the control of a central synchronization, monitoring and control station (SCC) where all the seismic data are finally gathered. The system is applicable to large-scale seismic exploration.

Abstract: Seismic data acquisition devices (BA) distributed in an exploration zone are divided into n groups (GA1 to GAn) and, therein, into sub-groups having each a specific frequency for communicating with a concentration unit (Ck) which is connected to a central station (1) through Hertzian channels or cables or optical fibers. Acquisition devices in the various subgroups communicate simultaneously with the corresponding concentration unit (Ck) during predetermined emission windows. The concentration unit collects the signals received from the acquisition devices to transmit them in series to station (1). The acquisition devices are adapted for delaying their own emission window according to the rank which has been previously assigned thereto within the respective subgroups thereof.

Abstract: The arrangement in the field of seismic emission-reception system changes as it progrsses along the profile explored, which modifies the respective distances between the source of seismic signals (S) and each of the siesmic receivers (Ri). In order to take account thereof, each of the acquisition boxes (Bi) used in the field for amplifying, digitizing and storing the siesmic signals received during each emission-reception cycle (or possibly a central station) is provided with a processor for determining automatically the gain to be assigned to the various amplifiers from all of the signals acquired and with selection rules taking into account the level of the signals and their evolution observed over several successive emission-reception cycles. The invention has an application in decentralized automatic control of acquisition devices.

Abstract: The system includes a plurality of acquisition devices (A.sub.i) for collecting signals received by receivers (Rk) and a central control, recording and processing station. This station manages the performance of the devices (A.sub.i), of successive signal acquisition cycles and thereafter the centralization thereof. In order to relieve the central station of part of the tasks thereof in case of a high volume of data to be collected and processed, acquisition devices are used which have management processors (2, M.sub.1, M.sub.2) and with complementary computing processors (7, M.sub.3) programmed for carrying out processings of the data before the transmission thereof. Various combinations of seismic signals, data compression, and quality controls are performed in real time during the phase of setting of the seismic equipment (seismic receivers and acquisition device electronics (CA1 to CAn) in the devices A.sub.i in the field), etc, immediately accessible to operators in the field.

Abstract: A method and an apparatus are applied to the seismic data received by receivers (Ri) distributed in the field and collected by acquisition boxes (Bi), in order to be transmitted to a central control and recording station (P), for example through hertzian channels. Digital words by adding to each N1-bit digitized signal sample, in each acquisition box, a n-bit coding suffix sufficient for detecting and correcting any transmission-related error. In order to eliminate the effect of long interferences, the method also comprises arranging the words in blocks, interleaving the words of each block at the time of the transmission, and forming digital symbols. A complementary sequence for reverse interlacing, deblocking and correcting possible errors brings the digital samples back to the original state thereof.

Abstract: A method for the automatic association, with seismic signals received by receivers (R1 . . . Rn) distributed on a site to be explored, of topographic data relative to the location of these receivers. The seismic signals are collected and stored by seismic acquisition devices (B1-Bn) which, after each seismic "shooting", transmit the signals successively to a central station 1. When the receivers are positioned in the field, each receiver is located by means of radiopositioning of the GPS type for example, and the position indications are introduced into an auxiliary memory of the corresponding acquisition device. After each repatriation of the data of a shooting, the indications are read in this memory and remain associated with those data at the time of the general grouping on the tape recorder of the central station.

Abstract: In a data acquisition for seismic exploration, where the terrain is rugged or includes natural features which prohibit satisfactory radio communication between a central control and recording system and a plurality of seismic data signal acquisition devices, a relay element and a transmission cable are provided so that those acquisition devices which are not capable of satisfactory radio communication with the central control and recording system communicate instead with the relay element either by transmission cable or radio transmission and the relay element in turn communicates with the central control and recording system either by radio transmission or transmission cable, respectively.

Abstract: A semi-sequential transmission method and system are provided making it possible for successive groups of seismic acquisition apparatus to communicate simultaneously, using several transmission frequencies, with a central seismic laboratory. Each of said apparatus comprises a frequency synthesizer capable, by means of switches, of setting itself to any one of different frequencies, and means for automatic distribution of the frequencies between the apparatus of the same group. Each of the apparatus, being given an order number dependent on its position along a seismic profile to be studied, determines the difference between its own order number and an order number which it receives by radio and which is that assigned to the first acquisition apparatus of its group. Depending on the difference measured and respecting certain limitations, each acquisition apparatus attributes to itself its own transmission frequency.

Abstract: A method is provided for the transfer to a central recording device of data corresponding to signals received by a set of seismic sensors which have been sampled, digitized and stored by a plurality of data acquisition apparatus and a device for implementing same, said process including the storage of data in static memories disposed in each of said apparatus, at the end of each recording session moving to the vicinity of each of them a mass memory associated with the device for transferring the collected data into this mass store over a high flow rate connection (cable, wide band short wave link, modulated light beams etc.) and the direct transfer of the data from the mass store to the recording device, a relatively narrow band radio link providing the direct transfer of recording or test data between the apparatus and the central recording system.

Abstract: A method and device are provided for initializing acquisition apparatus including the use of coded infrared rays for transmitting data and a control case, the initialization being provided by modulating a light beam in amplitude by means of a carrier signal, this latter being modulated both in frequency and in phase and the modulation depending on the initialization signals. A programmable processing unit delivers the digital data to an infrared ray transmitter, the light signals received in return from the acquisition cases provided with similar transmission means being received by an infrared receiver, decoded and reshaped before being applied to the processing unit.

Abstract: A system is provided for radio transmission between a central control and recording laboratory and spaced apart acquisition boxes in which relay transmission units are used for communicating with boxes which are directly inaccessible. It includes a centralization unit adapted for managing the exchanges of orders or data from the central laboratory with directly accessible boxes by means of a radio link in a first frequency band (f2), on the one hand and with the relay units by means of a radio link in another frequency band (f1). These latter manage the radio links with the inaccessible boxes by means of radio links at a frequency (f3) distinct from (f2). The relay units and the centralization unit are programmed for automatically managing the links between the central laboratory and any one of the boxes, whether they are direct or indirect, and, on the other hand, for reserving a part of the interrogation time of each box for the transmission of service data indicative of their correct operation.

Abstract: The method comprises detecting, during the combustion phase in at least one engine cylinder, the angular position of the crankshaft at which the value of the ratio of the volume of burnt gases to the overall gas volume in the cylinder reaches a preselected value, and adjusting the ignition timing to make said detected position of the crankshaft coincide with a predetermined position. The method also includes detecting for all cycles of operation the flame front in all the cylinders of the engine. The number of signals delivered by one of the detectors are counted for a specified number of cycles of operation of the engine and the average value of the change in angular position of the crankshaft during which time said signals are counted is determined. Accordingly, depending upon whether the number of signals counted in another cylinder falls below or above the count in the first cylinder, a corresponding reference signal is produced for controlling ignition timing.

Abstract: A process is provided for controlling the storage in a recording system of signal samples received successively over a transmission channel. The series of samples to be transmitted are subdivided into blocks comprising a given number of samples and each being provided with a digital timing word and a digital word containing the number of the block. Control units are used for detecting these two words and checking that the number of samples received is conformable and for controlling the access of the data received to the memory.

Abstract: In a system for seismic exploration, a narrow passband channel of relatively-slow transmission speed is used to transmit commands from a control station to one or more remote signal acquisition devices to initiate acquisition and processing of echo signals generated by triggering of a seismic signal generator at a selected reference time. To permit use of the slow speed transmission channel for transmitting commands without delay in the recording of the echo signals, a first command to initiate processing and recording of received signals is transmitted to the acquisition devices prior to the selected reference time by an amount of time at least equal to the transmission time of the narrow passband channel. This first command also initiates in each acquisition device the counting of signal samples which are being recorded at a predetermined rate.

Abstract: Device for the sequential transmission of signals by radio or by cable between a central control and recording station and local data acquisition apparatuses, comprising cables connecting said data acquisition apparatuses to the central station and radio transmission and reception means associated with each acquisition apparatus and with the central station, and switching means for establishing the cable connection and interrupting the radio connection between the central station and any particular apparatus for which said radio connection becomes defective as a result of obstacles on the path between the location of said apparatus and that of the central station.

Abstract: A method is provided for the automatic control of the ignition time in a spark ignition engine or the injection time in a compression-ignition engine wherein at least one typical phenomenon of the running conditions of the engine, such as the occurrence of the peak pressure in the cylinder within a certain angular interval of the crankshaft, or the passage of the flame front through a reference position of the combustion chamber is detected, and the detected measurements have an aleatory character. This method comprises the determination of a statistical value representative of at least P validated measurements, of said phenomenon occurring during at most Q cycles, and the use of said statistical value to modify the control time of the combustion initiation so that said statistical value takes a predetermined value corresponding to the desired running conditions.

Abstract: A method for amplifying multiplexed signals including the steps of amplifying each signal in different amplifiers, each having different amplification gains, selecting the amplified signal of optimum amplitude and digitizing the selected amplified signal wherein the selection is operated by a previous measuring of the digitized value of the signal, without amplification, considered as a reference signal.

Abstract: An accelerometer located on the cylinder head of an engine supplies a signal which is twice integrated thus giving a resulting signal whose peak value is detected. The spark advance is automatically adjusted so that this peak value occurs in a preselected angular position of the crankshaft. The advance may also be similarly adjusted based instead on the null point of the signal which results after an integration of the signal coming from the accelerometer.

Abstract: An accelerometer located on the cylinder head of the engine supplies a signal which is twice integrated thus giving a resulting signal whose peak value is detected. The spark advance is automatically adjusted so that this peak value occurs in a preselected angular position of the crankshaft.

Abstract: This device comprises, in combination, means generating a digital value equal to the difference between a number of cycles of the engine and the number of knockings detected during the period of said cycles and means controlling the spark advance point in response to said difference.