This paper presents an overview of the 5ESS 7 " system architecture. The administrative, communications, and switching modules are described, together with an overall view of the software architecture. Operations and maintenance aspects and a short discussion of evolutionary trends are covered.

The 5ESS™ switch is a world‐class switching exchange system. It is designed to handle many applications over a full range of office sizes and with a wide variety of customized services. Its modular hardware and software architectures and its feature‐customization capabilities provide this flexibility, and form the base for adding Integrated Services Digital Network (ISDN) capabilities. By the end of 1986, the 5ESS switch will begin offering ISDN services and, with simple hardware and software changes, will evolve from a conventional digital switch into an ISDN switch. This paper presents an overview of the 5ESS switch implementation plan. It describes the target user groups for the initial offering of ISDN services on a 5ESS switch, why the ISDN concept benefits these users, and what ISDN capabilities the 5ESS switch offers to meet their needs. It also describes the ISDN architecture of the 5ESS switch and how the ISDN capabilities are built incrementally on the switch's existing distributed, modular architecture.