Abstract: A control unit is used to set a first reading speed and a second reading speed of the information stored on the information medium as a function of a predetermined occupancy of the buffer below its storage capacity, for the purpose of reducing the number of returns. The drive motor which produces the reading speed is connected via a switch to the driver which drives it and, during the reduction of the reading speed to a predetermined value or until the occupancy of the buffer falls below a predetermined occupancy, the power supply to the drive motor which produces the reading speed, is reduced by means of a switch for the purpose of reducing the power consumption. Subcode information is preferably used to synchronize the data in the buffer after an interruption, and the buffer is preferably arranged between a first assembly for the pulse shaping of the signal read from the information medium and a second assembly for error correction.

Abstract: A device for electronic focusing of ultrasonic waves in which the focusing means comprise a hierarchized assembly of elementary circuits each provided with a delay line connected in parallel with a direct line to a centralizing unit and in which the time-delay of the delay line in a circuit is a function of the relative time-delay which must exist between the two cells or the two circuits connected to said circuit. It is shown that, in the invention, a technological advance is achieved by thus minimizing the maximum time-delays to be established in the case of each delay line.

Abstract: The present invention concerns a process for removing all ambiguity from the measurement by the Doppler effect of the speed of a target. It consists in obtaining a signal of Doppler shift relating to a series of ultrasonic pulses sent in the direction of the target and received after their reflection onto this target, the recurrence frequency of the pulses constituting an ambiguity limit of these speed measurements, wherein the measured Doppler shift is transposed by modulating the signal received by a signal at a frequency called determination frequency, so as to bring from a known value the spectral components to be analyzed in the useful measuring band and after measuring the true speed values are worked out by adjunction of a correction that depends upon the determination frequency that is used, this process being applicable to measuring the speed of blood in the medical field.

Abstract: The invention relates to a method for characterizing the structure of a medium in which the ultrasonic absorption coefficient of the medium is measured. In order to perform a spectral analysis of this absorption, the spectrum of the signal reflected after it has been transmitted is evaluated by means of an autocorrelation method. Application: medical practice.

Abstract: The invention relates to a method of measuring the flow parameters of a fluid, and to a device utilizing this method, in which the autocorrelation function of the signal transmitted back by a particle of the fluid in motion is calculated. The mean speed and the variance of the flow are calculated by calculating the derivations of orders 1 and 2 of this autocorrelation function.