| 摘要 |
PURPOSE:To attain suitable transmission restriction by measuring the time from calling to the end of call tone connection, comparing a measured value with a preset delay time, supervising an abnormal calling from an obtained call tone connection delay time measuring value and restricting the calling of unimportant subscriber when the abnormal call is detected. CONSTITUTION:The call tone connection delay time measuring circuit 4 uses a measuring end signal reception to complete the mesurement of the call tone connection delay time and stores the result of measurement in a built-in register. An exchange program reads a call tone connection delay time via the register. The call tone connection delay time mesured by the circuit 4 is read by an abnormal call supervisory program and is compared with the specified value of the call tone connection delay time and when the value is more than the specified value, the number of times detecting the value over the specified value is counted, and when the detection number of times is consecutive for the prescribed number of times, it is regarded as the abnormal calling state to restrict the call. |
