Etablissement Public De Diffusion Dit 'telediffusion De France'

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Telediffusion De France

Centre National D'etudes Des Telecommunications

Michel G Mathieu

Pierre Charbonnel

Jean-Claude Pacaud

Andre J Le Rodallec

A videodisc reader head positioning control system stores the keyed-in address for a desired picture frame and compares it to the track address for the frames during passage of the reader head toward the desired frame. Logic circuitry distinguishes the difference between the desired address and the address of the head's current position in order to control the head positioning unit at a fast, intermediate, or precision speed. Upon reaching the desired address, the logic circuitry maintains the position of the head for stop frame display of the picture information.

Disc and videodisc reader head positioning control system

A digital signal formed from successive words representing quantized samples of sound information and comprising silent periods is synchronized with a local reading clock. For that, the words are stored in a random access memory as they arrive, they are read at the frequency of the local clock and the filling rate of the store is permanently determined. A comparator compares this rate with a given range. If the filling rate is greater than a maximum threshold or less than a minimum threshold, the contents of the memory are modified at the first silent interval which appears.

Process and apparatus for synchronization of digital signals

The consequences of the loss of a packet are attenuated in a digital data communication apparatus using packet switching by structuring the digital data as multibit words into frames having a fixed length l and assembling the frames into packets all having the same predetermined length L=kl, where k is a predetermined integer. Continuity index words incremented by one each time a new frame or packet is assembled may be located into the frame locking word or the packet prefix. Then the number of packets which are lost may be determined at the receiver location by monitoring the successively received index words. When the digital data represent successive samples which are correlated, for instance when such samples represent a sound, substitution data may be generated at the receiver location and used in place of the missing data.

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Hermitage, France

Michel G Mathieu