| 摘要 |
PURPOSE:To prevent mis-reception of a PB signal from a subscriber attended with voice message transmission by predicting and cancelling bypass component of a voice message to a 4-wire side output of a 2/4 wire conversion means. CONSTITUTION:A voice storage circuit 60 generates white noise prior to transmission of a voice message to a subscriber under the control of a processor 30 for a prescribed time and a weight coefficient of a tap of an FIR filter 41 is optimized, that is, adaptive control is implemented so that the residual component of an adder 42 of an echo canceller 40 is minimized. The FIR filter 41 receiving the voice message outputs a predicted bypass component corresponding to the tape weight coefficient. The predicted value is approximated to the bypass component to the 4-wire output of a 2/4-wire conversion circuit 10. Thus, the residual component resulting from the subtraction of both input signals to the adder 42 reaches a very low level and the result is sent to a PB signal receiver 61. |
