| 摘要 |
PURPOSE:To reduce the number of component parts, to decrease power consumption and to easily make a circuit integrated by providing a first voltage detection means and a second voltage detection means for detecting the electric state of a line, a signal addition means for adding outputs from the first and the second voltage detection means and an amplification means for amplifying the output from the addition means. CONSTITUTION:The electric state of the subscriber's line 101 is detected by the first and the second voltage detectors 109 and 110 and signals detected by the detectors 109 and 110 are added by the signal adder 123 and made to feed back to a first and a second nodes through the amplifiers 107 and 108. By supplying a specified DC current to the subscriber's line 101 and monitoring the DC current, the removal of in-phase noises is executed. Thus the number of component parts can be reduced and the power consumption can be decreased, and moreover the circuit is easily integrated. |
