| 摘要 |
PCT No. PCT/GB92/02102 Sec. 371 Date Jun. 10, 1994 Sec. 102(e) Date Jun. 10, 1994 PCT Filed Nov. 13, 1992 PCT Pub. No. WO93/10623 PCT Pub. Date May 27, 1993A digital coder receives either speech or audio-band data. When receiving speech this is coded by a digital speech coder and formatted into frames with parity bits. If modulated data are present this is recognized by a detector which routes the signals instead via a demodulator. Parity bits are generated from the same frame portions but parity is inverted so that a parity checking unit at a receiver can readily recognise the change. Preferably means are provided to insert into data frames codewords identifying the start and end and indicating the type of modulation in use. Additional detectors and demodulators can be added for different types of modulation. Such coded signals are decoded by performing parity checks on received frames to produce a parity indication signal of a first data mode sense or a second speech mode sense. In a data mode, the received signals modulated in accordance with a predetermined modulation scheme are provided as an output and in a speech mode the received signals are decoded to provide a speech output.
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