| 摘要 |
PURPOSE:To reduce a malfunction rate at the detection of a PB signal with respect to a voice signal by using a difference between amplitude fluctuation of a voice signal and a PB signal and discriminating it not to be the PB signal when the ratio of the input signal amplitude shares a certain value with respect to the maximum value of the input signal amplitude within a prescribed time so as to inhibit the detected output of the PB signal. CONSTITUTION:An amplitude fluctuation monitor section 25 and a gate 26 are provided. The amplitude fluctuation monitor section 25 detects an input signal amplitude larger than a threshold level resulting from multiplying a prescribed ratio with a maximum value of the amplitude within a prescribed time of an input signal and generates an output. Moreover, the gate 26 inhibits the output of a PB signal detection circuit 1 when an output is generated from the amplitude fluctuation monitor section 25. Thus, the amplitude fluctuation monitor section 25 detects it that the input signal exceeds a threshold level signal generated from the maximum value of the amplitude in a prescribed time and discriminates it to be the absence of a PB signal at the production of the detection signal thereby inhibiting the output of a PB signal detected output generation logic section. Thus, mis-detection rate of the PB signal is reduced. |
