SUBSCRIBER LINE INTERFACE CIRCUITRY WITH COMMON BASE AUDIO ISOLATION STAGE

摘要

Methods and apparatus for coupling outgoing analog audio signals to a subscriber line are described. A subscriber line interface circuit apparatus couples an outgoing audio signal to the subscriber line through a common base isolation stage. In one embodiment, linefeed driver control signals for controlling battery feed to the subscriber line are received on the same signal lines as the outgoing audio signal. In various embodiments, the common base isolation stage comprises a plurality of bipolar junction transistors coupled in a common base configuration or a plurality of field effect transistors coupled in a common gate configuration.