| 摘要 |
PURPOSE:To provide high impedance against an alternating current and also to attain IC-implementation by semiconductors, by making even DC output resistance by inserting an element with a positive resistance coefficient into an artificial inductor in an electronic switchboard subscriber's circuit. CONSTITUTION:With the handset of telephone set 7 off the hook, an electric current from DC power source 5 flows through transistor TR10b', compensating element 8', TR10a', output terminal 2', line 6', telephone set 7, line 6, output terminal 2, TR10a, compensating element 8, and TR10. Viewing two two-terminal circuits from the line side and electric power source side at this time, they become inductive because of the impedance conversion of capacitors 11 and 11' and high impedance can be obtained against an AC signal. As the DC resistance of the line decreases, the electric current from the electric power source increases and resistance values of compensating elements 8 and 8' also increase to reduce the electric current, keeping the DC output resistance nearly constant. |
