All wire connections, repeater chains or radio relay connections with which the clock can be transmitted via the interface together with the data stream are referred to as clock-transparent connections. Clock-transparency must be valid in both directions. PCM2 connections, for instance, are clock-transparent in one direction only. The number of repeaters is only limited by the jitter and drift values provided by the route and which must comply with the input requirements. This must always be researched and checked for leased lines. Unstructured leased lines (i.e. without frame) are normally transparent if PDH technology is used. The procedure in figure is based on the assumption that transparent connections are used for the assignment of the priority values.