1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU$)4!,G0G0%8#(!.%3$)4!,G0G0,/#!, G0G0#/-“).%$ G0G042!.3)4!.$G0G0).4%2.!4)/.!,G0G0%8#(!.%3G0).42/$5#4)/.G0G0!.$G0G0 tone generation; conferencing facilities.Their location is dependent on the function itself an
2、d the exchange configuration.3.4 Exchange design objectives (Recommendations Q.541, Q.542, Q.543 and Q.544)3.4.1 General design objectives (Recommendation Q.541)This includes the general design objective principles, availability and hardware design objectives as well as thedesign objectives associat
3、ed with the operation of an exchange in an Integrated Digital Network. The latter encompassestiming and synchronization design objectives.Timing comprises the generation and distribution of timing signals and includes timing of outgoing signals. Itenables those parts of the exchange which form the s
4、witched path of a connection to operate synchronously.Synchronization will depend on the national synchronization plan and exchange timing arrangements.Exchanges will usually extract synchronizing information from one or more incoming bit streams or a separatesynchronization network and use this to
5、adjust the timing signals generated in the distribution within the exchange.3.4.2 Operations and maintenance design objectives (Recommendation Q.542)This covers the operations and maintenance design objectives including network management controls, alarmhandling and subscriber line maintenance and t
6、esting.3.4.3 Performance design objectives (Recommendation Q.543)Exchange performance design objectives are defined for guiding system design and for comparing thecapabilities of different systems. (Recommendations relating to provisioning and operational performance of exchangesin the network are c
7、overed in the E.500-E.543 Series.)3.4.4 Exchange measurements (Recommendation Q.544)Measurements that may be used for planning, operation, maintenance and network management of exchangesand their associated networks are described. The measurement data consists primarily of event counts and trafficin
8、tensity levels experienced by the various traffic handling elements of the exchange.3.5 Transmission characteristics (Recommendations Q.551 to Q.554)3.5.1 Transmission characteristics of digital exchanges (Recommendation X.551)This includes the general definitions associated with Recommendations Q.5
9、51 to Q.554, and transmissionparameters from a total exchange perspective such as absolute group delay and the transfer function for jitter andwander. These Recommendations define, for any connection which may be set up by a local, combined, transit orinternational exchange, the necessary levels of
10、transmission performance to conform with overall objectives for thecomplete user-to-user connections in which the exchange may be involved.4 Fascicle IV.5 - Rec. Q.5003.5.2 Transmission characteristics at 2-wire interfaces (Recommendation Q.552), 4-wire interfaces(Recommendation Q.553) and digital interfaces (Recommendation Q.554)These cover the detailed transmission characteristics of the various types of interface that may be provided ona digital exchange.
