This chapter describes signaling system , the first-generation commonchannel signaling system. There are two versions of this system, both of which were first deployed in the mid-1970s. CCITT [l, 23 is still in use in the international network, on a number of transatlantic and transpacific trunk interofice signaling (CCIS), defined by the Bell groups. Common-channel System, has been used in the . toll network [3,4], but has now been replaced by the North American version of signaling system | Signaling in Telecommunication Networks. John G. van Bosse Copyright 1998 John Wiley Sons Inc. ISBNs 0-471-57377-9 Hardback 0-471-22415-4 Electronic SIGNALING SYSTEM NO. 6 This chapter describes signaling system the first-generation commonchannel signaling system. There are two versions of this system both of which were first deployed in the mid-1970s. CCITT 1 2 is still in use in the international network on a number of transatlantic and transpacific trunk groups. Common-channel interoffice signaling CCIS defined by the Bell System has been used in the . toll network 3 4 but has now been replaced by the North American version of signaling system . There are many similarities between the CCITT and CCIS. In this chapter we use the acronym SS6 when discussing matters that are common to both versions. The definition of SS6 took place at the time that telecommunications was still synonymous with telephony and long-distance trunks were carried on analog voiceband transmission channels of FDM multiplexed transmission systems. In SS6 a signaling data link usually consists of a pair of these analog voiceband channels. However SS6 signaling data links can also be implemented as pairs of digital PCM transmission channels. SS6 signaling can be used for FDM analog and PCM digital trunks which may be equipped with circuit-multiplication equipment CME see Section . However the signaling data links have to be carried on transmission channels without CME. SS6 was designed originally for call control applications only. Around 1980 the Bell System expanded CCIS to include query-response transactions between exchanges and centralized network databases. 126 SIGNALING LINKS 127 Analog Channels ----------------------Signaling Link ------------------------ Figure SS6 signaling link a analog signal b digital bit stream. SIGNALING LINKS Signaling Link Components Figure shows a SS6 signaling link in which the data link consists of a pair of
