Abstract: Signalling and localisation device for an individual in the sea, including an ultrasonic wave transmitter constituting an individual alarm unit carried by the individual in the sea designed to transmit carrier waves of primary signals; a surface surveillance means arranged on the surface of the sea and provided with: a submersed antenna capable of picking up the primary signals transmitted by individual alarm unit; means of transmitting secondary ultrasonic signals, these transmission means: means capable of calculating the position of individual alarm unit as a function of the ultrasonic signals received in response to secondary ultrasonic signals and of converting this information into the coordinates of a global positioning system; a unit for transmitting radio waves capable of sending signals representing these coordinates to a mobile or fixed alarm processing centre equipped with a radio receiver.

Abstract: Signalling and localisation device for an individual in the sea, including an ultrasonic wave transmitter constituting an individual alarm unit carried by the individual in the sea designed to transmit carrier waves of primary signals; a surface surveillance means arranged on the surface of the sea and provided with: a submersed antenna capable of picking up the primary signals transmitted by individual alarm unit; means of transmitting secondary ultrasonic signals, these transmission means: means capable of calculating the position of individual alarm unit as a function of the ultrasonic signals received in response to secondary ultrasonic signals and of converting this information into the coordinates of a global positioning system; a unit for transmitting radio waves capable of sending signals representing these coordinates to a mobile or fixed alarm processing centre equipped with a radio receiver.

Abstract: A frequency/phase detector for a reference signal with a fixed frequency and a second signal with a variable frequency comprises essentially a frequency discriminator, already known, in which the output signal of a frequency-dependent phase-shifting circuit centered on said fixed frequency is applied, not directly to a demodulator circuit but through a summing circuit that receives in addition said reference signal.

Abstract: The disclosure relates to the measurement of small time lags between a signal edge and a reference instant defined by another signal edge. It consists of the use of a signal edge for the prompting, by means of shock-excited resonating filters, of the appearance of two sinusoidal signals in quadrature constituting the components of a complex vector with a substantially constant module, the phase of said complex vector developing linearly in the course of time, and in deducing, from the value of this phase at the sampling reference instant, the value of the time lag between the reference instant and the signal edge. It can be applied more particularly to the measurement of short time lags of a few nanoseconds.

Abstract: The field of the invention is that of frequency doublers. More precisely, the present invention concerns a low noise frequency doubler, which in particular can operate at frequencies of the order of several GHz, or even of several tens of GhZ. According to the invention, the frequency doubler, operating in particular in the microwave range, is of the type including means of phase shifting to obtain two signals with a phase difference of 180.degree. from an input signal of frequency F and means for amplifying each of these two signals, the output signal of frequency 2F formed by adding the said amplified signals, the said means of amplification cooperating with means for varying the gain of the said means of amplification to make the gain of the said means of amplification practically proportional to the amplitude of the said amplified signals.

Abstract: A recirculation circuit for repetition of an analog pulse signal provided with a return loop from an output divider and with an input adder for reinjecting the signal into a delay circuit connected between the adder and divider. An active circuit having a nonlinear gain characteristic is further inserted in the loop for producing a loop gain which is less than or greater than unity according as the amplitude of the signal is lower than or higher than a predetermined threshold value. So as to substantially attenuate the parasitic signals. The recirculation circuit may be further provided with a limiter circuit for delivering the repeated signal at constant amplitude.

Abstract: A sample-and-hold circuit has an input terminal connected to a source of analog voltages to be stored, this terminal being connected during a sampling phase via a first switch to an output terminal and to an input of a first amplifier working into a storage capacitor by way of a second switch also closed during that phase. The capacitor is tied to one of two differential inputs of a second amplifier, the other differential input being connected to the output of the first amplifier upon closure of a third switch during a holding phase in which the first and second switches are open.

Abstract: A system for bringing the frequency of an oscillator under the control of the frequency of the carrier of a pulse wherein a parameter characteristic of the carrier frequency value is measured throughout the duration of the pulse, the measurement result is stored, the same parameter is measured in respect of the frequency to be controlled, and the control is carried out after the pulse by comparison of the second measured parameter with the first and stored measured parameter.