| 摘要 |
PURPOSE:To decide a sound signal with a continuous and single tone by deciding the frequency component of an input signal and discriminating between a sound signal and a MODEM signal. CONSTITUTION:A signal to be discriminated is converted into a 2's complement type PCM signal through an encoding circuit 1, an output signal of a delay circuit 12 is subtracted from the PCM signal by a subtracting circuit 10 to find out an error signal and prescribed arithmetic processing is executed by a positive/negative deciding device 13, a delay circuit 14j, a multiplexer 15j, an integrating circuit 16j, and the 6th non- circulation type digital filter 11. Consequently, respective factors ai, j of the filter 11 are changed so that the output signal of the filter 11 becomes a signal approximate to the input signal. At that time, the frequency component of the sound signal is concentrated into a band near a prescribed frequency and the frequency component of a MODEM signal is dispersed, so that the converged values of the factors ai, j are different in accordance with the kinds of the signals and the factors a1, j, a2, j are differentiated. Thereby, integrated outputs a2, j are converted into binary values by a comparator by using a value between the outputs a2, j at the time of the sound signal and the MODEM signal as the threshold and the binary value is smoothed 21 to discriminate the input signal.
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