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: A recirculatory analog signal sample amplifier having at least a first prtermined gain is provided with error determining means for recirculating a zero input signal with a second predetermined gain, thereby obtaining an error signal, and correction means to deduct from an incoming sample, before its circulation, a value proportional to the error signal.

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.