This International Standard contains requirements necessaryforthesynchronization of PISNs. Timing within adigital private network needs to becontrolled carefullyto ensure that the rateof occurrence of Slips between PINXs within the PISN,and the public switched networks is sufficiently low not to affect unduly the Performance of voice transmissions, or the accuracy or throughput (if errored data require re-transmission) of non-voice Services. Requirements are also based upon the interconnection of digital private telecommunication networks via digital facilities in the public (switched or not) telecommunication networks. This International Standard is one of a series of technical Standards on telecommunications networks. This International Standard with its companion Standards fills a recognized need in the telecommunications industry brought about by the increasing use of digital equipment and facilities in private networks. lt is useful to anyone engaged in the manufacture of digitalcustomerpremisesequipment(CPE)forprivatenetworkapplications,andtothosepurchasing,operatingorapplying digital CPE to digital facilities for Private Integrated Services Networks (PISN). This International Standard establishes technical criteria necessary in the design of a synchronization plan for a PISN. Compliance with these requirements would be expected to result in a quality PISN synchronization design.