| 摘要 |
PURPOSE:To eliminate the division loss among the charging trunk circuit, the general talking trunk circuit and the trunk line each, by providing the polarity inversion pulse circuit at the trunk line side of the network as well as an additional circuit to the terminal unit side each. CONSTITUTION:Polarity inversion pulse circuit 12 having the functions to supply the talking current and transmit the polarity inversion pulse is provided at the trunk line side of network 3. At the same time, additional circuit 14 which gives termination to the talking current given from general talking trunk circuit 13 and makes only the talking signal pass through is provided at the terminal unit side. Then circuit 14 is connected to circuit 13 via the 1st network bus to transmit the talking signal to public telephone 1. On the other hand, circuit 12 is connected to telephone 1 via the 2nd network bus to supply the polarity inversion pulse and the talking current. In such way, the polarity inversion pulse circuit is installed in an intensive way, thus eliminating the division loss of the general talking trunk circuit and the trunk circuit. |
