| 摘要 |
PROBLEM TO BE SOLVED: To provide a polarity inversion circuit where production of a speech noise due to polarity inversion is suppressed by suppressing a rapid inversion of a current between ring and tip lines caused in the case of the polarity inversion. SOLUTION: The polarity inversion circuit 1 comprises a polarity inversion control circuit 2, polarity inversion changeover time setting circuits 3, 4, a Ring line battery level transmission control circuit 5, a Ring line ground transmission control circuit 6, a Tip line battery level transmission control circuit 7, and a Tip line battery level ground transmission control circuit 8. When the polarity of the Ring line and the Tip line is inverted or restored, the control circuit controls so as to stop transmission of a battery level of one line and transmit a ground level gradually within a prescribed time. Moreover, after confirming the arrival of one line to a ground level, the transmission of the ground level to the other line is gradually stopped and to transmit the battery level. |
