| 摘要 |
<p>Circuit apparatus included in a subscriber line circuit for creating a variable line connection impedance for the subscriber line circuit. This comprises a two wire-four wire converter, i.e. a subscriber line interface circuit (SLIC) and a subscriber line audio processing circuit (SLAC). In the latter there is conventionally included a controllable impedance (Z) comprising a digital filter. A resistor (RT) which can be controllable, or a controllable amplifier (Za) is connected across the four wire side of the SLIC to form the resistive part of the termination impedance (Zi) while the already available digital filter in the SLAC forms the reactive part. An adding circuit (A1) superposes the current contribution from the resistive onto the reactive part.</p> |
