| 摘要 |
The transverse and longitudinal termination impedances of a subscriber line interface circuit may be independently controlled. The equivalent termination impedance of a subscriber line/trunk appearing to the central office can be adusted upward or downward from a lower resistance value, with longitudnal balance being determined by the matching of feed resistors. The circuit is implementable as a monolithic integrated circuit having low power dissipation, improved power bandwidth requirements, and lower voltage breakdown requirements for integrated circuits; all resulting in an improved telephone line interface circuit. Voltage or current feedback to synthesize the proper ac transverse termination impedance from a known dc resistance, is utilized the feed resistors in a telephone line circuit. The transverse and the longitudinal termination impedance are determined by choice of feed resistance value. The independent control of transverse impedance is achieveable as a result of the feedback circuitry being nonresponsive to longitudinal signal. |
