Common Channel Interoffice Signaling: No. 4 ESS Application

No. 4 ESS, a large-capacity toll switching machine, was originally designed to handle two basic address signaling systems, Dial Pulse (DP) and Multifrequency (MF). With the introduction of common channel signaling into the domestic toll network, No. 4 ESS included as part of its initial offering the Common Channel Interoffice Signaling (CCIS) capability. Other papers discuss the basic system architecture, 1 hardware,2 and call-handling software3 of the No. 4 ESS with emphasis on the DP and MF signaling systems. This paper deals with the specific hardware and software design associated with CCIS. Section II describes the overall CCIS design constraints, system architecture and hardware as it applies to No. 4 ESS. Section III describes the CCIS software organization and functional implementation.