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Search for ITU-T Recommendations and Supplements: ITU-T Recommendations by series Select a series of Recommendations A series: Organization of the work of ITU-T D series: General tariff principles E series: Overall network operation, telephone service, service operation and human factors F series: Non-telephone telecommunication services G series: Transmission systems and media, digital systems and networks H series: Audiovisual and multimedia systems I series: Integrated services digital network J series: Cable networks and transmission of television, sound programme and other multimedia signals K series: Protection against interference L series: Construction, installation and protection of cables and other elements of outside plant M series: Telecommunication management, including TMN and network maintenance N series: Maintenance: international sound programme and television transmission circuits O series: Specifications of measuring equipment P series: Terminals and subjective and objective assessment methods Q series: Switching and signalling R series: Telegraph transmission S series: Telegraph services terminal equipment T series: Terminals for telematic services U series: Telegraph switching V series: Data communication over the telephone network X series: Data networks, open system communications and security Y series: Global information infrastructure, Internet protocol aspects and next-generation networks Z series: Languages and general software aspects for telecommunication systems

Q series: Switching and signalling Q.1-Q.3: Signalling in the international manual service Q.4-Q.59: International automatic and semi-automatic working Q.60-Q.99: Functions and information flows for services in the ISDN Q.100-Q.119: Clauses applicable to ITU-T standard systems Q.120-Q.499: Specifications of Signalling Systems No. 4, 5, 6, R1 and R2 Q.500-Q.599: Digital exchanges Q.600-Q.699: Interworking of Signalling Systems Q.700-Q.799: Specifications of Signalling System No. 7 Q.800-Q.849: Q3 interface Q.850-Q.999: Digital subscriber Signalling System No. 1 Q.1000-Q.1099: Public Land Mobile Network Q.1100-Q.1199: Interworking with satellite mobile systems Q.1200-Q.1699: Intelligent Network Q.1700-Q.1799: Signalling requirements and protocols for IMT-2000 Q.1900-Q.1999: Specifications of signalling related to Bearer Independent Call Control (BICC) Q.2000-Q.2999: Broadband ISDN Q.3000-Q.3999: Signalling requirements and protocols for the NGN Q supplements: Supplements to ITU-T Q-series Recommendations