Abstract: An atomic clock of the type comprising a quartz oscillator, a tube contaig a material, the atoms of which have an hyperfine spectral transition, control means capable of generating, from the quartz oscillator, a control signal of a frequency that corresponds to the hyperfine spectral transition, and of applying this control signal to the tube to cause interaction between this signal and the atoms of the material contained in the tube, and feedback means that are sensitive to the response of the tube and are adapted to modifying the frequency of the quartz oscillator so as to substantially center the frequency of the control signal on the frequency of the hyperfine spectral transition, wherein the control means are adapted to cyclically generate test signals, the controlled frequency of which is located outside the Ramsey peak.

Abstract: The encoder comprises a pendulum (P) mounted to rotate about a horizontal is (O-O) which is substantially coaxial with a reference axis (R-R) of an index disk and which carries vertical optical detector equipment (T.sub.M.pi.E, T.sub.M.pi.R, T.sub.MOE, T.sub.MOR), optical guidance means (M.sub.1, M.sub.2, M.sub.3, M.sub.4, T.sub.5) fixed to the pendulum and suitable for guiding radiation generated by an optical transmitter (T.sub.M.pi.E) towards an associated optical receiver (T.sub.M.pi.R) along a predetermined optical path intersecting the disk (D), and a liquid level forming device (L) fixed to the pendulum (P) and inserted on the optical path upstream from the said point of interception between the optical path and the disk, the said optical guidance means (M.sub.1, M.sub.2, M.sub.3, M.sub.4, M.sub.

Abstract: The invention relates to the radio-electrical transmission of accurate timing-mark signals. A space-diversity electrical connection is formed between a station having one single antenna and a station having two antennae and one of the stations is equipped with a receiver device which combines into one composite timing-mark signal the different repetitive timing-marks decoded and rectified from high-frequency signals which have traversed several spatial propagation paths. A common automatic gain control circuit weights the decoded and rectified timing marks according to a weighting which diminishes with the level of high frequency reception. Preferably the rectification of the timing marks is carried out non-linearly.

Abstract: Measurement of distance is carried out by transmitting a VHF wave train crising a sinusoidal signal modulated by phase inversion in accordance with a pseudo-random sequence, at a receiver shifting a like second sequence until it coincides with the received sequence, re-transmitting a signal modulated by the second sequence, receiving the second sequence and shifting a like third sequence until it coincides with the received second sequence, and measuring the phase shift between the third sequence and a like reference sequence.

Abstract: An electronic angular coder for theodolites or the like, comprising a rotng disk bearing a series of engraved radial markings, a stationary detector, and a mobile detector. An approximate measure of the offset angle between a stationary detector and a mobile detector is accomplished by counting the markings passing in front of the heads. Fine measures of the shift in phase between the passage of a marking in front of the mobile detector and the fixed detector are also obtained.

Abstract: An infra-red telemeter comprises a pilot oscillator 1 and a controlled oscillator 2 kept in phase with the pilot oscillator 1. The controlled oscillator 2 provides the modulation frequency for transmission, either directly for fine measurement or via a counter 11 which divides by M. for coarse measurement, while the pilot oscillator 1 provides a heterodyne frequency, either directly or after division by N in a counter 17, respectively. After the received modulation signal has been mixed with the heterodyne frequency, a phase detector 18 compares the phase of the mixed signal with the phase of a reference low frequency obtained by the frequency of oscillator 1 being divided by H in counter 17. The phase servo loop operates continuously, in the case of both fine and coarse measurement.

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: In a digital angle coder, a revolving disc bears a first series of marks ularly spaced around its axis, capable of being read by two diametrically-opposed fixed heads, and a second series of marks equal in number to the first, regularly spaced around the axis and capable of being read by two diametrically opposed movable heads. Each of the heads includes, for example, a grid reproducing a portion of the series of marks, a photo-emission element and a photo-receiving element. A first auxiliary mark may be read by a fixed auxiliary head and a second auxiliary mark may be read by a movable auxiliary head.

Abstract: The invention relates to an electromagnetic velocity pickup of the horizol seismometer type, wherein an oscillating mass is elastically suspended as an inverted pendulum with the aid of a deformable system of the articulated parallelogram type. The pickup is characterized in that the suspension comprises rigid beams and at least one elastic pivot.

Abstract: A method of and apparatus for differential mode navigation in a sequential system of radio-navigation by phase reception. A transmitted amplitude-modulated radio-navigation carrier wave is phase or frequency modulated, this modulation being effected by a low-frequency subcarrier signal which is itself so phase modulated sequentially in accordance with phase corrections that each phase correction appears approximately simultaneously with the phase concerned. The phase corrections are derived from the difference between the phase received from each fixed station of the system and theoretical phases which should be received from that station. At a standard radionavigation receiver, the subcarrier signal modulated by the corrections is recovered, and the phase corrections are so applied to the received phases that each phase undergoes the phase correction received at the same instant.

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.

Abstract: Pointwise positioning apparatus for positioning a movable assembly includes small strip defining a series of positions corresponding to an electrical absolute position coding which co-operates with a movable assembly to produce a pulse signal when the movable assembly is or passes a predetermined coded position. A general control motor is coupled mechanically to a step motor, and a logic circuit actuates the general control motor until a first passage through the predetermined position, whereupon the general control motor is actuated in the opposite sense until the movement of the movable assembly reverses, and then the step motor is actuated until the movable assembly again reaches the predetermined position.

Abstract: An electronic device for amplifying, with automatic gain control by discr values, analogue signal samples and thereafter preferably effecting analogue-to-digital conversion of the samples, consists of an amplifier circuit, a comparator circuit, and a delay store circuit. The amplifier has a basic gain during a gain control or gain ranging operation, and supplies an output sample amplified with sufficient gain to bring it into the region of a predetermined voltage. The comparator circuit compares the output of the amplifier circuit with a reference and supplies an output in accordance with the result of the comparison. For analogue-to-digital conversion the amplifier circuit supplies for an input signal U an output signal 2U - VQ, where VQ is the quantification voltage, or, in other embodiments a signal 2U.