| 摘要 |
PURPOSE:To detect the abnormality even to an intermittent voice signal by providing a level detection circuit detecting the level of a reference voice signal and a comparison voice signal. CONSTITUTION:A level comparator 1 outputs the abnormality detection signal 12 when a level difference between the level of a comparison voice signal 11 and the level of a reference voice signal 10 reaches a preset value of above. A level detection circuit 2 detects the levels of the reference voice signal 10 and the comparison voice signal 11 and outputs a normal detection signal when both signals reach a reset level or above. When the abnormality detection signal 12 is received, a flip-flop circuit 3 is set and outputs a fault signal 14 to a delay circuit 4 and when a normality detection signal 13 is received, the flip-flop circuit 3 is reset and stops the output of the abnormality signal 14. Thus, even in the case of the voice signal when the signal level is intermittingly zero as a time signal tone, the abnormality is detected. |
