| 摘要 |
PCT No. PCT/SE83/00329 Sec. 371 Date Apr. 27, 1984 Sec. 102(e) Date Apr. 27, 1984 PCT Filed Sep. 14, 1983 PCT Pub. No. WO84/01249 PCT Pub. Date Mar. 29, 1984.An apparatus for applying current to a subscriber line telephone set (RL) with associated two-wire line connected to a telephone exchange. The apparatus includes two analog amplifiers (5,6) each with its output connected to one of the two wires of the line, and feeding out on the line the combined DC current and current representing the speech signal. A DC/DC converter supplies voltage to an at least one of the amplifiers. To form a control voltage to the DC/DC converter, a cascade connection of a differential amplifier (1), a lowpass filter (2) and an adding circuit (3) are arranged between the line connection terminals and the control signal input of the DC/DC converter. |
