| 摘要 |
<p>An apparatus and method for determining an abnormal condition of a telephone line. A tone generator (10) applies a signal having a frequency of least 20,000 hertz to the telephone line (12, 14) to determine a reference test signal amplitude under normal conditions. The same tone generator (10) can apply a similar signal to the telephone line (12, 14) to determine an abnormal test signal amplitude under abnormal conditions. The difference in the test signal amplitudes indicates the abnormal condition of the telephone line (12, 14).</p> |
