Etablissement Public De Diffusion Dit 'telediffusion De France'

L'etat Francais

L'etat Francais, Represente Par Le Ministre Des P.t.t. (centre National D'e

Roger Motsch

Germain Lolivier

Claude Sechet

Francoise Roussel

A teletext receiver incorporating a demodulation circuit, a data demultiplexing circuit, a memory, a microprocessor and a numbering keyboard. The inventive receiver also comprises an early article acquisition decision circuit disposed between the demultiplexing circuit and the memory. This circuit incorporates a shift register with five cells, a storage module having a first group of three storage cells able to store three bytes, a second group of three storage cells able to store three bytes, a two-bit flip-flop, a logic comparison circuit incorporating a first group of three byte comparators, a second group of three byte comparators, an article start code detector, and a comparison synthesis logic circuit connected to the six byte comparators, to the detector and to the flip-flop. This circuit supplies an opening or closing control signal applied to the control input of the memory. The microprocessor loads in an appropriate manner the storage cells with bytes defining a page to be selected and bytes defining a threshold, such that all the articles whose classification bytes exceed this threshold, bring about the appearance of the memory opening signal. The microprocessor checks after each data transmission cycle the state of the memory in order to raise or lower the threshold, or leave it unchanged.

Teletext receiver

A numerical or digital transmission system uses an adaptative coding, of log information, which is sampled and transformed by an orthogonal transformation. The coding has a rate of data flow or delivery, which is reduced by orthogonal transformation with an adaptative threshold. In each scanning field, the binary elements of the coefficients are obtained by a basic coding with a quantification pitch 2S, (S being a whole number either positive or null). A complementary coding is transmitted. The complementary coding is obtained by adding binary elements of weights 2S-1 for each one of the coefficients, until the transmission capacity of the channel is filled. The coefficients are taken in chronological order. The invention is applicable to digital television, but also the coding may be used for transmission of high fidelity sound.

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Mordelles, France

Roger Motsch