No. 4 ESS: Peripheral system

The No. 4 ess peripheral system economically performs essential switching and signaling functions. A modern time-division switching network has been developed to meet rapidly growing traffic demands and provide a basis for the all-electronic telecommunications network of the future. Common-channel interoffice signaling (ccis) provides high-speed interprocessor communication via data link. Signal processor units perform routine signaling tasks such as scanning and digit collection, effectively increasing the main processor's capacity. To a greater degree than in previous systems, the vital man-machine interfaces are enhanced with sophisticated interactive capability.