Abstract: The invention relates to data acquisition devices making it possible, by the use of elastic surface waves, to mark the coordinates of a stylus (7) making a line on the surface (2) of a piezoelectric plate (1).The invention relates to a device in which the measuring surface (2) is provided with roughnesses or unevennesses of negligible size compared with the wavelength of the surface waves. The stylus (7) also comprises a member (8) for supplying a marking substance (10).The invention is more particularly applicable to the remote transmission of graphic symbols and to the processing of digital data representing such symbols.

Abstract: An optical pickup which performs the function of a light pen is capable of point detection of elastic waves propagated by electrochemical transducers in a direction parallel to the surface of a writing table. The table is constituted by a plate of refractive material placed within an optical polarizing cell which prevents emergence of incident radiation produced by a light source. The pickup receives that portion of the radiation which emerges from the cell by virtue of the birefringence induced within the plate by the elastic wave trains issuing from the transducers.

Abstract: An addressing unit for accessing two sequences of instructions quasi-simultaneously, the two sequences of instructions being prerecorded in a single memory. Addresses for the two sequences appear alternately at the address output of the addressing unit at a predetermined clock rate. During a single clock period, the addressing unit receives data for calculating the next address in the first sequence while it is calculating the address of the next instruction in the second sequence. In the following clock period the addressing unit calculates the address of the next instruction in the first sequence while it is receiving data for calculating the address of the next instruction in the second sequence, and so on. In this manner, the unit is simultaneously receiving data for one sequence and calculating an address for the other sequence.

Abstract: The invention relates to piezoelectric devices employing a piezoelectric layer deposited on a substrate devoid of piezoelectric properties at ambient temperature. The device in accordance with the invention is provided with a piezoelectric layer made from a mono-atomic crystalline material, namely selenium. The invention is applicable to the excitation of surface elastic waves along non-piezoelectric substrates, to the excitation of bulk elastic waves and to the detection of infrared radiations.

Abstract: A microprogrammable control unit to be associated with a memory in which there have been pre-recorded two sequences of micro-instructions relating to two faces (digital systems) to be coupled and to outside resources adapted to emit control signals necessary for these two digital systems is provided. The control unit comprises at least an addressing unit for the memory adapted to the quasi-simultaneous operation of the two sequences, internal resources comprising at least for each face an input register, an output register of data and a counter and common to the two faces a multiplexer of the signals indicating the states of the internal resources and of the external resources, instruction registers for memorizing codes furnished by the micro-instruction extracted from the memory and a transcoding device controlling the resources, the addressing unit and the multiplexer as a function of the codes of micro-instructions with which data are associated.