| 摘要 |
<p>PURPOSE:To obtain a subscriber line DC supply circuit used even by a subscriber line in loop state or in one line state by switching to use the comparison voltage of a voltage detecting circuit in both DC feedback circuits depending on whether the loop state or the one line state of the subscriber line. CONSTITUTION:When a load is connected between a tip line and ground, a switch S2 of a tip line voltage detecting circuit 5T is connected to the position (f). In this connecting state, the tip line voltage detecting circuit 5T detects a potential difference between the tip line and ground, a polygonal line characteristic is decided by a DC feedback circuit 4T for tip line from the detected potential difference, and the corresponding current is supplied from a power supply circuit 1. When the tip line and the ring line are formed in a loop, a switch S1 of a ring line voltage detecting circuit 5R is thrown to the position (a) and a switch S2 of the tip line voltage detecting circuit 5T is connected to the position (c), and -Va is applied to both. In this case, the tip line voltage detecting circuit 5T and the ring line voltage detecting circuit 5R detect respectively a potential difference to the voltage -Va to apply feedback.</p> |
