| 摘要 |
PURPOSE:To relieve the load of processing for a processor by converting an intermitted AC signal such as a multi-frequency signal in an exchange into a rectangular wave signal, using a counter to measure the presence period of the rectangular wave signal and transferring the measured content to the processor. CONSTITUTION:A rectifier circuit 1 and the 1st, 2nd counters 2, 3 are provided and an AC signal such as a PB signal and a MF signal is converted into a rectangular wave signal by the rectifier circuit 1. The 1st counter 2 starts counting a clock signal at the rising of the rectangular wave signal, the count is stopped at the falling of the rectangular wave signal and the 2nd counter 3 starts counting the clock signal. Then the count is stopped at the falling of the next rectangular wave signal, interruption is applied to the processor 4 to transfer the count of the counters 2, 3 to the processor 4 as the consecutive time of the AC signal and a pause time. When the consecutive time t1 and the pause time t2 are prescribed values or over, the processor decides the state as the correct interrupting time of the AC signal, and when the pause time is a very short time such as a time t6, it is judged as a hit of the AC signal. |
