No. 4 ESS: Mass Announcement Subsystem
T. W. Anderson, J. H. Bobsin, R. F. Cook, L. Gingerich, M. A. Marouf, R. J. Milczarek · Bell System Technical Journal · 1981
This paper describes a new hardware subsystem developed to provide mass announcement capabilities for No. 4 ESS. The subsystem records, stores, and plays back recorded announcements for distribution through the No. 4 ESS switching network. Announcements are stored in digital form on a moving-head disk system. Microprocessors are used for control of disks and of interfaces. Duplicated hardware ensures high reliability, and extensive self-testing capability is provided