Abstract: Bit generator for determining a secret encryption key and a corresponding process, the generator having a memory with one memorization cell and measurement and reference bits, and a calculation device connected to the memory, such that a bit applied at an input of the bit generator makes another bit appear at an output thereof. Such a generator is applicable to cryptographic systems and methods.

Abstract: A flat screen display system uses a two-dimension surface acoustic wave ("SAW") scanning. The flat screen is made of a piezoelectric substrate coated with a layer of piezoluminophor powder. Four SAWs having two by two nonparallel directions are launched along the piezoelectric surface. The first of the two SAWs is pulsed and the third one has a constant amplitude. The fourth SAW is modulated by the information to be displayed. With respect to the modulated SAW, the pulsed SAWs are launched with a delay that is determined by the distance to be covered by the modulated SAW, for reaching the point which the current modulation corresponds to.

Abstract: The invention relates to a filter for demodulating signals modulated in frequency in binary manner by the switching of two frequencies F.sub.a and F.sub.b.On a piezoelectric crystal, is produced two surface wave filtering units, each comprising a transmitting transducer and a receiving transducer with interdigitated electrodes. The number of electrodes of the receiving transducer of the first unit is substantially equal to twice (2F.sub.a -F.sub.b)/2(F.sub.b -F.sub.a ) with a spacing of v/(2F.sub.a -F.sub.b), in which v is the propagation rate. In the case of the second unit, this number is approximately twice (2F.sub.b -F.sub.a)/2(F.sub.b -F.sub.a) with a spacing of v/(2F.sub.b -F.sub.a). The receiving transducers are preferably subdivided in each case into two juxtaposed transducers, whereof one is set back with respect to the other by a distance of approximately v/4F.sub.a for the first unit and v/4F.sub.b for the second.

Abstract: A common channel charge transfer recursive filter has two delay lines, in which charges are transferred in opposite directions. Exchange bridges having two sections extend between the lines. Each section feeds a predetermined charge fraction to one of the two downstream electrodes with charges flowing from the two upstream electrodes. The charge transfer is controlled by a three-phase system (.phi.1, .phi.2, .phi.3). Split memory electrodes and the exchange bridges are connected to the first phase (.phi.1) bus. A transfer electrode is in each gap between an exchange bridge and a memory electrode and is connected to the second phase (.phi.2) bus. A second transfer electrode is connected to the third phase (.phi.3) bus. The gap between a memory electrode and the next exchange bridge is occupied by a transfer electrode connected to the second phase (.phi.2) bus and by a transfer electrode connected to the third phase (.phi.3) bus.

Abstract: An elastic surface wave recursive filter comprising: at least one delay line formed by two elastic surface wave transducers, such line being looped on itself externally by an amplifier, a means for introducing an elastic surface wave into such line, such means being connected to an input of the filter, and a third transducer having the form of a transversal filter, the transducer being coupled to said line and connected to an output of the filter. The transfer function of the filter is the form P(z)/Q(z), the numerator and the denominator being independant.

Abstract: An elastic surface wave recursive filter comprising: one passive resonator formed by two tuned transducers, a means for introducing an elastic surface wave into such resonator, such means being connected to an input of the filter, and a third transducer having the form of a transversal filter, the transducer being coupled to the resonator and connected to an output of the filter.The transfer function of the filter is of the form P(z)/Q(z), the numerator and the denominator being independant.

Abstract: An analog-to-digital converter comprising a plurality of conversion stages, each of said stages containing a charge transfer device constituted by a storage electrode mounted at the input, by a storage electrode mounted at the output and by intermediate auxiliary electrodes, the area of the output electrode being K times smaller than that of the input electrode, said converter being characterized in that it contains a means for multiplying charges in the ratio K/1, said means being inserted between the output electrode of each stage and the input electrode of the following stage, and in that all the stages are identical.

Abstract: The surface elastic wave device is an integral part of an analog-digital converter with intermediate frequency conversion. It is comprised of the acoustical part of a 4-pole surface elastic wave oscillator, a surface elastic wave reflector with track shifting working as a filter assembly and comprising one supply track and several return tracks having different angular frequencies, the reflector operating as a plurality of filters, and output transducers overlapping the return tracks and connected to detectors producing the digital information. Many types of reflectors and output transducer assemblies are described. The invention is useful with analog-digital converters having medium access times.