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Abstract

The method consists in momentarily replacing the data transmitted by a digital data link with a digital message comprising two non-consecutive sequences, with the first sequence being a prefix sequence and the other sequence being a suffix sequence. The period of time separating the prefix and suffix sequences is variable and encodes remote signalling data. FIG. 2 shows a message transmitter circuit fitted in digital link equipment for operation at a very high data rate, and provided with a circuit (6') for detecting and handing alarms and with a circuit (3) for recovering the bit rate from the digital stream. A pattern generator (10) serves to generate a 1000 pattern and its 0111 complement from the recovered check rate. An oscillator (20) has a period which defines the time interval separating the prefix sequence and the suffix sequence. This oscillator controls a sequencer (25) which in turn controls a prefix sequence building circuit (30) and a suffix sequence building circuit (40) both of which act via logic gates on a circuit for selecting pattern types and on switching means (19) for inserting the selected sequence into the digital stream instead data.

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First Claim