| 摘要 |
PROBLEM TO BE SOLVED: To prevent the deterioration of the maximum data rate of an XDSL signal and/or the sound quality of a POTS signal by deciding the communication state of the call of a communication system and allocating overhead voltage in accordance with the state for transmitting the POTS signal and the XDSL signal. SOLUTION: A processor 135 judges a POTS state, an XDSL state and the loop state of a communication system 100, judges the voltage request of a line driver 125, controls a resistance value or other means and changes an overhead voltage level by a detection circuit and the processor function of a telephone switch 105. Overhead voltage is voltage quantity required for driving an AC signal through a communication system 100 without saturating the amplification circuit of a line driver 125. An overhead voltage signal has amplitude selected for driving a POTS signal from a POTS interface 115, an XDSL signal from an XDSL interface 120 or the combination of both signals.
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