| 摘要 |
Direct bit extraction from a scrambled bit stream for a digital transmission system in which a bit stream is divided into consecutive transmission frames, extra bits are inserted in given bit position of each transmission frame, the bit stream is scrambled in a transmitter terminal station and transmitted via a plurality of regenerative repeaters to a receiver terminal station in which the transmitted bit stream is descrambled and the inserted extra bits are selected from the bit stream. Both the scrambler and the descrambler include a generator for generating a given fixed scramble pulse pattern and a transmission clock pulse counter which, on attaining its final counting position, supplies a setting pulse which adjusts the pulse pattern generators in the scrambler and the descrambler to an initial generation state. By choosing a fixed relation between this final counting position and the number of bit positions per transmission frame it is possible to select with simple means the extra bits, inserted in the consecutive transmission frames, in the repeaters and the receiver terminal station without the necessity of first descrambling the received scrambled bit stream.
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