| 摘要 |
PURPOSE:To prevent wrong detection of the disengaged line signal and to catch the disengaged line signal swiftly and correctly by detecting the disengaged line signal by use of the outputs of the voice zone element detection circuit out of the control signal and the control signal element detection circuit, together with the output of the signal demodulation circuit. CONSTITUTION:In case the disengaged line signal has not been detected, an output exists in the control signal element circuit 40, while an output does not exist in the voice zone element detection circuit 39 out of the control signal, and when the disengaged line singal has appeared in the output of the signal demodulation circuit 38, it is judged that the disengaged line signal has been detected. And after the disengaged line signal has been detected, in case an output does not exist in the circuit 40, or an output exists in the circuit 39, it is judged that the disengaged line signal has not been detected yet, and the operation is shifted to detection of the disengaged line signal. Thus, it is possible to prevent wrong detection of the disengaged line signal, and to catch the disengaged line signal swiftly and correctly. |
