This Recommendation is only applicable to international data transmission links and systems for PDH applications. The requirements described in this Recommendation should form the basis for all digital test measurements associated with these types of applications. The performance limits are also applicable to the international portions of international leased circuits that are supported by an international data transmission system and that have a PDH digital interface at the Customer's premises. Allocations of performance between international and national portions are covered, but those between Network Operators within the national portion require further study. Recommendations M.1370 and M.1375 describe the Bringing-Into-Service and Maintenance procedures respectively for international data transmission links and systems, while Recommendations M.1380 and M.1385 describe similar procedures for international PDH leased circuits supported by those systems. These Recommendations are to be applied in conjunction with the performance objectives, allocations and limits described in this Recommendation. This Recommendation addresses the performance of leased circuits with a PDH digital presentation at the Customer's premises. Another Recommendation is being developed for performance of SDH leased circuits. For leased circuits with an analogue presentation, the performance limits of Recommendations M.1020, M.1025 or M.1040 are applied as appropriate.