Architecture, Design, and Development of the System 75 Office Communications System

AT&T-IS System 75 is a new customer-premises digital communications system. It is designed to complement the larger AT&TIS System 85 in the intermediate size range of 20-400 stations and makes use of the same terminals and adjuncts. System 75 utilizes a distributed switching and control architecture and employs VLSI for a compact cost-effective realization. Integrated voice and data communications are supported with full voice conferencing capabilities and high-speed data switching. A process and message-based software architecture supports a large number of features and services, including a flexible user-oriented maintenance and administration capability, accessible from a local or remote system management terminal. This paper describes the system, the switch, common control, software architecture, system management capabilities, and product testing methods.