| 摘要 |
<p>A telephone-line-connection monitoring device comprises a switch to disconnect the ringing circuit of a subscriber telephone and a ring detector circuit to monitor the central office connection for ring indications. When a ring indication is recognized, the ringing circuit switch is closed to allow ringing currents to reach the bell. The ringing circuit switch in its open condition allows a battery-voltage threshold monitor across the subscriber line connection to quickly detect a line fault. Otherwise, the large capacitor in the ringing circuit would artificially prop up the voltage and cause a slow bleed-down to the threshold voltage after a fault occurred.</p> |
