| 摘要 |
<p>PURPOSE:To use electronic parts which can be converted to an IC by inserting in series a switch into terminal impedance provided on a part which is not connected directly to a call line. CONSTITUTION:A terminal impedance element 7 is provided on a part which is not connected directly to a call line 5, the impedance of a call current supplying circuit 6 from a telephone set 4 side is set, and a switch 8 is inserted in series to the element 7. Also, by opening the switch 8, the impedance of the current supplying circuit 6 from the telephone set 4 side is set sufficiently higher than the terminal impedance of the telephone set 4 side, and a mutual call between party line telephone sets contained in the same subscriber's circuit can be executed.</p> |
