PURPOSE:To enable relatively long recording near the incidental abnormality phenomenon point by operating the recorder for the specified time only after the abnormality detection point in response to the abnormality detection signal obtainable from an abnormality detector or its delay signal. CONSTITUTION:The data input from an analog signal line 1 are subsequently stored in a memory 3 and are recorded in a recorder 5. On the other hand, in response to the abnormality detection signal obtainable from an abnormality detector 6 by way of the analog signal line 1, the delay time delayed for the specified time from the abnormality occurrence point is set in a delay time setting circuit 7 and the sampling frequency is reduced from 10kHz to 0.5kHz in response to this delay time. In response to this, the writing and reading speed in the memory 3 is also reduced. After the abnormality detection point, the recorder 5 is operated for the foregoing specified time only.
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