| 摘要 |
PURPOSE:To reduce a computing quantity and a memory capacity for the detection of a training signal and to improve the reliability of signal detection, by providing a detector consisting of a DTF(discrete Fourier transform means), an integrator, and a comparator. CONSTITUTION:The detector 15 provided in a switching device 14 is constituted of the DTFs 20a and 20b, the integrator 21, and the comparator 22. The DTFs 20a and 20b extract the power of f4 and f5 out of the frequency components which constitute the training signal, and output power signals W4 and W5 to the comparator 22. The comparator 22 compares the signals W4 and W5 with a power signal Wb in which the whole of the training signals from the integrator 21 are integrated, and decides whether it is a modem signal, and outputs a decided result as a detecting signal to a switching circuit 16. The switching circuit 16 introdues the signal of a modem or a telephone set to respective signal processing block of a modem mode and a voice mode by being controlled by the signal from the comparator 22, and sends out those outputs of the blocks to an external line. In such a way, it is possible to reduce the computing quantity and the memory capacity and to improve the reliability of the signal detection.
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