| 摘要 |
PURPOSE:To detect the point of time of signal stop quickly, by obtaining a total power of sound and signals and detecting the point of time of stop of receiving signals with this total power, in a device detecting the signals transmitted on the same communication channel with the sound. CONSTITUTION:The sound and signals incoming to an input terminal 1 are applied to a signal detecting circuit 2, a sound detecting circuit and a power detecting circuit 6 at the same time. Each detected output of the circuits 2, 3, 6 is applied to a signal discriminating circuit 4 to detect the presence of the signals. In this case, the signal detecting circuit 2 is a circuit using the discrete Fourier transformation, where the point of time of signal stop is detected with a delay. A signal discriminating circuit 4 detects the point of time of signal stop with the stop of an output of the power detecting circuit 6 when the output of the signal detecting circuit exists and decreases the output of the signal detecting circuit 2. |
