| 摘要 |
<p>PURPOSE:To make it possible to measure the accurate characteristics of a line, by mechanically connecting an apparatus having arbitrary input impedance to the line but electrically separating the same from the line. CONSTITUTION:A circuit 16 of which the resistor Rz is changed by applied voltage Vi is inserted between an apparatus 12 having arbitrary input impedance Ri and a line 11. In usual, voltage VO is applied to the line 11 and a current is supplied to the apparatus 12 but the resistor Rz of the circuit 16 is 0OMEGA, that is, a continuity state and exerts no effect on current supply action. Voltage having polarity inverse to that of the applied voltage VO is utilized in an arrival call signal in the case of a telephone line but, even in this case, because the resistor Rz of the circuit 16 is 0OMEGA, there is no effect. When voltage VM lower than voltage VO is applied to the line 11, the resistor Rz of the circuit 16 comes to infinity OMEGA, that is, a disconnection state. Therefore, the impedance Ri of the apparatus is not observed from terminals 14, 15 and the insulating resistance Rx of the line 11 can be accurately measured.</p> |
