Racal-Milgo Limited

Laurence F Turner

Henry H Parrish

John W Bailey

To enable binary data to be differentially encoded into symbols (waves) for transmission the data is applied in n-bit data-words to produce symbols which, when displayed in a phasor-diagram, are in three groups in three 120.degree.-phase-sectors respectively, the number and dispositions of the symbols in the three sectors being the same. The encoding is such that, depending upon the data-word to be transmitted the sector in which a symbol is produced is rotated by 0.degree., 120.degree. or 240.degree. relative to the next preceding sector containing a symbol. In some embodiments one of the 2.sup.n possible different data-words is applied to produce an absolute symbol of zero amplitude. At a receiver the received symbols are decoded having regard to the 0.degree., 120.degree. and 240.degree. differential sector-rotations.

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Bishop's Stortford, United Kingdom

Laurence F Turner