| 摘要 |
PURPOSE:To suppress detour of a signal by forming a matching impedance for 2-wire/4-wire conversion by a ladder circuit comprising capacitors and resistors so as to change continuously the impedance by means of a changeover switch. CONSTITUTION:The matching impedance is obtained by switching parallel branching of a ladder circuit comprising capacitors and resistors by means of the changeover switch 11. The switching of the switch 11 is performed by a control circuit according to the line impedance. In short-circuiting input terminals 9, 10, the impedance viewed from a point P is 2C independently of the selected position of the switch 11. Further, the impedance of the ladder circuit is equivalent to that of a transformer. Further, the winding ratio is dependent on the position of the switch 11. The suppressing effect of the detour of a signal is improved by changing continuously the matching impedance. |
