This document describes a highly integrated subscriber line interface kit for PABX and key system applications. It implements all key elements of the BORSCHT function, including integrated zero crossing balanced ringing injection, elimination of external relay and centralized ringing generator, zero noise injected on adjacent lines during ringing sequence, low power in standby and active modes, battery feed with programmable limiting current, parallel latched digital interface signaling functions, low number of external components, integrated thermal protection, and integrated over current protection.
