| 摘要 |
checking an operation of hook-offs; judging a polarity inversion of hook off by the ring signal; displaying a time by counting elapsed time when the polarity is inverted; judging time elapsing; outputting an alarm signal when a predetermined time is elapsed; judging completing of a call; recording the time and charge by calculating the elapsed time; and repeating the above time counting step when a phone line is busy.
|
