A Software Programmable CMOS Telephone Circuit

A mixed Analog-Digital IC combining the speech and signalling functions for an analog telephone on a 2μ CMOS chip will be described. New features such as software programmable level control, dc characteristics, input impedance and transhybrid balancing offer a flexible system-solution for the different international requirements with a minimum number of external components. This features enable telephone manufacturers to produce a quality feature phone with a minimum number of components, and therefore with high reliability and low cost.