| 摘要 |
<p>PURPOSE:To prevent the occurrence of a hit on each channel due to outgoing or incoming of other channels during communication by changing the way of receiving when the voltage of the 1st polarity is applied and that of the 2nd polarity is applied to a subscriber line. CONSTITUTION:A line terminator 1 of station side is provided with a feeding polarity changeover switch 7, loop current detecting circuit 13 detecting a subscriber line loop current, and a logical circuit 14 inputting a loop current detecting signal outputted by the said circuit 13 and a display signal representing the state of communication corresponding to a channel given from an exchange so as to transfer the connecting state of the feeding polarity changeover switch 7. A receiving power supply 6 of a subscriber side line terminal device is started when the voltage of the 1st polarity is applied to the subscriber line and received through a parallel connecting circuit of switches 9A, 9B closed from the start of call to the end of call and also from the response to the end of call of any subscriber equipment when the voltage of the 2nd polarity is applied.</p> |
