| 摘要 |
<p>A telephone interface circuit with impedance termination during call pauses, comprising: a first and a second terminals of a telephone line; a branch connected to the first terminal, across a decoupling capacitor, and to the second terminal, and furthermore comprising an intersection node; the branch comprises a first switch and a first impedance resistor between the first terminal and the intersection node and a second switch and a second impedance resistor between the second terminal and the intersection node; the intersection node is connected to the ground across a third switch; the first switch, the second switch, and the third switch are controlled by a control unit by means of a first, a second and a third control lines respectively. The circuit furthermore comprises a ring signal detector that is connected to a microprocessor unit capable of activating the control unit in the interval in which the circuit must be terminated for CLID (Calling Line IDentification) transmission. <IMAGE></p> |
