ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å@8Ø'@8Ø'Å Ð SECTION 1 © INTRODUCTION AND FIELD OF APPLICATION Áà1ÁÓÓÃÃContents of Recommendation Q.500Äă Áà#ÁDIGITAL LOCAL, COMBINED, TRANSIT AND INTERNATIONAL EXCHANGES,ƒ Áà/ÁINTRODUCTION AND FIELD OF APPLICATIONƒ 1.ÁHÁIntroduction 2.ÁHÁField of application 3.ÁHÁThe Q.500©Series of Recommendations ÁàAÁƒ ÁàAÁ*ƒ ÁàAÁƒ Áà@Á*     *ƒ ÃÃRecommendation Q.500ÄÄ Áà#ÁDIGITAL LOCAL, COMBINED, TRANSIT AND INTERNATIONAL EXCHANGES,ƒ Áà/ÁINTRODUCTION AND FIELD OF APPLICATIONƒ 1.ÁHÁÃÃIntroductionÄÄ Ð ° ÐÁHÁThis series of Recommendations Q.500©554 applies to digital local, combined*, transit and international exchanges for telephony in Integrated Digital Networks (IDNs) and mixed analogue/digital networks, and also to local, combined, transit and international exchanges in an Integrated Services Digital Network (ISDN). ÁHÁThe series of Recommendations comprises: Q.500ÁHÁIntroduction and field of application Q.511ÁHÁExchange interfaces towards other exchanges Q.512ÁHÁExchange interfaces for subscriber access Q.513ÁHÁExchange interfaces for operations, administration and maintenance Q.521ÁHÁExchange functions Q.522ÁHÁExchange connections, signalling and ancillary functions Q.541ÁHÁDesign objectives © General ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Ð h Ð* ÃÃNoteÄÄ © A "combined" digital exchange is one which includes both local exchange   and transit exchange functions (see definition 1005 in Recommendation Q.9). Q.542ÁHÁDesign objectives © Operations and Maintenance Q.543ÁHÁPerformance design objectives Q.544ÁHÁExchange measurements Q.551ÁHÁTransmission characteristics of digital exchanges Q.552ÁHÁTransmission characteristics at 2©wire analogue interfaces Q.553ÁHÁTransmission characteristics at 4©wire analogue interfaces Q.554ÁHÁTransmission characteristics at digital interfaces. ÁHÁConsiderations have been primarily on exchanges utilizing, at least in part, time division switching techniques. However, these Recommendations are implementation independent, and other system implementations using alternative techniques (e.g. space division switching) may be possible, which would meet the requirements of these Recommendations. 2.ÁHÁÃÃField of applicationÄÄ ÁHÁThese Recommendations are intended to be applied as indicated below. 2.1ÁHÁÃÃApplication and evolution to the ISDNÄÄ ÁHÁThe selection of features, functions and interfaces to be provided in a digital local, combined, transit or international exchange in a particular network application will be determined by the administration concerned. Reference to a function in these Recommendations, including their diagrams, does not imply that it will necessarily be provided in every exchange type or configuration. Similarly, it is possible that some functions may be provided which are not mentioned. 2.2ÁHÁÃÃRelationship of design performance requirements to operationalÄÄ ÃÃperformance ÂHHÂrequirementsÄÄÆÆ Ð ` Ð Ð H ÐÁHÁPerformance requirements as defined in this series of Recommendations should be considered as design objectives for systems under the conditions stated in the Recommendations. These conditions are defined by such parameters as average circuit occupancy, busy hour call attempts, etc. They should be distinguished from the operational performance requirements which administrations establish for exchanges operating in their particular environment. ÁHÁFurther clarification of this point can be obtained in Recommendation G.102. 3.ÁHÁÃÃThe Q.500©Series of RecommendationsÄÄ 3.1ÁHÁÃÃExchange Interfaces (Recommendations Q.511, Q.512 and Q.513)ÄÄ ÁHÁThe interface functions defined are those necessary for interworking with digital and analogue transmission systems on both circuits to other exchanges and on subscriber lines, and with telecommunications management networks. 3.1.1ÂðHÂÃÃCharacteristics of exchange interfaces towards other exchangesÄÄ ÃÃ(Recommendation Q.511)ÄÄÆÆ ÁHÁThis Recommendation describes the exchange interfaces used to transmission facilities towards other exchanges. It applies to digital local, combined, transit and international exchanges for telephony in integrated digital networks (IDN) and mixed (analogue/digital) networks, and also to local, combined, transit and international exchanges in an integrated services digital network (ISDN). 3.1.2ÂðHÂÃÃCharacteristics of exchange interfaces for subscriber accessÄÄÆÆ ÂHHÂÃÃ(Recommendation Q.512)ÄÄÆÆ Ð ` ÐÔ w.ÔŒÁHÁThe Recommendation describes the subscriber side interface characteristics. It applies to digital local and combined exchanges for telephony in Integrated Digital Networks (IDN) and mixed (analogue/digital) networks, and also to local and combined exchanges in an integrated digital network (ISDN). Ð ° Ð3.1.3ÂðHÂÃÃExchange interfaces for operations, administration and maintenanceÄÄ ÃÃ(Recommendation Q.513)ÄÄÆÆ Ð X ÐÁHÁThe interfaces defined are those necessary for transmission of messages associated with operations, administration and maintenance of the exchange. ÁHÁThese interfaces include OAM interfaces between the exchange and the following: OAM systems, mediation devices, user workstations, and other network elements. 3.1.4 Á  ÁÃÃInterfaces to non©voice handling facilitiesÄÄ ÁHÁThe need for the Recommendation of interfaces between digital transit, local and combined exchanges and non©voice handling facilities remains for further study. (An example of such a non©voice facility is a packet switched data node.) Attention is drawn to Recommendation X.300 which describes the general principles for interworking between public data networks and also to the I.400/I.500©Series Recommendations for interworking between ISDN and other dedicated networks. 3.2ÁHÁÃÃExchange functions (Recommendation Q.521)ÄÄ ÁHÁThis Recommendation covers the definition of the principal exchange functions to support services and includes a description of an exchange functional model. 3.3ÂàHÂÃÃExchange connections, signalling and ancillary functionsÄÄ ÃÃ(Recommendation Q.522)ÄÄÆÆ ÁHÁThis Recommendation covers the following functions: ÁHÁa)Âh   ÂConnections through an exchangeÆÆ ÁHÁThis section includes the switch block(s), the characteristics associated with connections through exchanges and a set of diagrams showing typical types of connection. ÁHÁA connection through an exchange may include one or more stages of time and/or space division switching, providing a path for transmission through the exchange. ÁHÁb)Á   ÁSignalling ÁHÁSignalling includes reception of call©related and other information, interaction with the call control function and transfer of information to subscribers and network(s) as required. ÁHÁSignalling may involve common channel and/or channel associated signalling. ÁHÁc)Á   ÁControl and Call Handling ÁHÁControl and call handling includes initiation, supervision and termination of most actions in the exchange. ÁHÁCommands are initiated and information passed/received to/from the other functions within the exchange. ÁHÁControl functions may be contained in one block or distributed throughout the exchange. ÁHÁd)Á   ÁAncillaries ÁHÁExamples of such functions are: ÁHÁÁ  Á©Á øÁrecorded announcements; ÁHÁÁ  Á©Á øÁtone generation; ÁHÁÁ  Á©Á øÁconferencing facilities. ÁHÁTheir location is dependent on the function itself and the exchange configuration. 3.4ÂàHÂÃÃExchange design objectives (Recommendations Q.541, 542, 543 and 544ÄÄ)ÆÆ 3.4.1ÁHÁÃÃGeneral design objectives (Recommendation Q.541)ÄÄ ÁHÁThis includes the general design objective principles, availability and hardware design objectives as well as the design objectives associated with the operation of an exchange in an Integrated Digital Network. The latter encompasses timing and synchronization design objectives. ÁHÁTiming comprises the generation and distribution of timing signals and includes timing of outgoing signals. It enables those parts of the exchange which form the switched path of a connection to operate synchronously. Synchronization will depend on the national synchronization plan and exchange timing arrangements. ÁHÁExchanges will usually extract synchronizing information from one or more incoming bit streams or a separate synchronization network and use this to adjust the timing signals generated in the distribution within the exchange. 3.4.2ÂðHÂÃÃOperations and maintenance design objectives (Recommendation Q.542)ÄÄÆÆ ÁHÁThis covers the operations and maintenance design objectives including network management controls, alarm handling and subscriber line maintenance and testing. 3.4.3ÁHÁÃÃPerformance design objectives (Recommendation Q.543)ÄÄ ÁHÁExchange performance design objectives are defined for guiding system design and for comparing the capabilities of different systems. (Recommendations relating to provisioning and operational performance of exchanges in the network are covered in the E.500©E.543©Series.) 3.4.4ÁHÁÃÃExchange measurements (Recommendation Q.544)ÄÄ ÁHÁMeasurements that may be used for planning, operation, maintenance and network management of exchanges and their associated networks are described. The measurement data consists primarily of event counts and traffic intensity levels experienced by the various traffic handling elements of the exchange. 3.5ÁHÁÃÃTransmission characteristics (Recommendations Q.551©4)ÄÄ 3.5.1ÂðHÂÃÃTransmission characteristics of digital exchangesÄÄ ÃÃ(Recommendation Q.551)ÄÄÆÆ ÁHÁThis includes the general definitions associated with Recommendations Q.551©4, and transmission parameters from a total exchangeÔ w.Ô perspective such as absolute group delay and the transfer function for jitter and wander. These Recommendations define, for any connection which may be set up by a local, combined, transit or international exchange, the necessary levels of transmission performance to conform with overall objectives for the complete user©to©user connections in which the exchange may be involved. 3.5.2ÂðHÂÃÃTransmission characteristics at 2©wire interfacesÄÄ ÃÃ(Recommendation Q.552), 4©wire interfaces (Recommendation Q.553) andÄÄ ÃÃdigital interfaces (Recommendation Q.554)ÄÄÆÆ ÁHÁThese cover the detailed transmission characteristics of the various types of interface that may be provided on a digital exchange.