| 摘要 |
PURPOSE: To easily discriminate the erroneous operation of a user and a true fault by counting the abnormal signal from a corresponding line state circuit end transmitting a fault alarm when the count value reaches a preliminarily determined count value. CONSTITUTION: When a line interface 11-0 is in its using state, the state of a signal '1' is transmitted from the incoming call detection part and the signal is supplied to an AND circuit 212 and a NOT circuit 214. For the period when the state of the signal '1' is continued, the circuit 212 makes the pulse from a pulse oscillator 211 pass and the number of the passed pulse is counted by a pulse counter 213. At this stage, when the pulse frequency of the oscillator 211 is set to one pulse for every 10 seconds and the line interface 11-0 is continuously used for 38 seeds, the count number of the counter 213 becomes 3. This count value is successively supplied to a comparator circuit 215 and is recorded, the value is compared with preliminarily set maximum and minimum allowable values. If the values are within the range, a normal signal is transmitted, and if the value becomes the outside of the allowable range, an abnormal signal is transmitted. |
