"PACT" - A Programmable Analog CMOS Transmission Circuit for Electronic Telephone Sets

A CMOS circuit is presented which performs all analog interface functions to a standard telephone subscriber line including DC and AC termination, send and receive amplification, anti-side-tone network, line loss compensation, and dialing control. All transmission parameters are software programmable and are loaded into the IC during hook-off or, if necessary, during conversation. It is fabricated in a standard CMOS process for digital circuits and may be combined with a microcontroller core for a one chip telephone.