Abstract: Apparatus for obtaining seismic data or information in the field comprises electrical communication paths established between seismic detectors distributed over the ground, and a digital seismic data recorder. Each of the paths comprises a pre-amplifier, various filters, a regulable-gain amplifier, and finally a digitizer, or the paths have these elements at least partly in common. The digitizer operates by carrying out random weighing; it comprises a pseudo-random generator and at least part of the contents of this generator is loaded in parallel into a register. The pseudo-random number thus obtained is converted into an analogue signal and is used for weighing a sample of the seismic signal in a comparator. This gives a single bit each time, which is then recorded in the recorder.

Abstract: An installation for the multiplexed transmission of signals from seismic eivers, each associated with a respective multiplexing circuit, connected in series in a transmission line between a generator of first pulse signals and a registration station. Each receiver is followed by a digitiser and each multiplexing circuit includes means allowing the first pulse signals to pass without modification, at least one shift register, capable of being filled with digital information from the associated receiver and connected in series in the transmission line, means for detecting the first pulse signals coupled upstream in the transmission line, and means for applying clock signals to the shift registers after each detection of the first pulse signal.