scope:

This final draft European Telecommunication Standard (ETS) outlines requirements for timing devices used in synchronising network equipment that operates according to the principles governed by the Synchronous Digital Hierarchy (SDH). These requirements apply under the normal environmental conditions specified for SDH equipment. Typical SDH equipment contains a slave clock linked to a master, or a primary reference clock. The logical function of the SEC is described in figure 2 of prETS 300 462-2 [3]. In general the SDH Equipment Clock (SEC) will have multiple reference inputs. In the event that all links between the master and the slave clock fail, the equipment should be capable of maintaining operation (holdover) within the prescribed performance limits contained within this ETS.

Slave clocks used in SDH equipment shall meet specific requirements in order to comply with the jitter specifications given in ETS 300 417-1-1 [9] for plesiochronous tributaries.

The case where clock performance, as described in DE/TM-03017-4 [4], is required in SDH equipment is outside the scope of this ETS.

NOTE: Parts 4 and 6 of this ETS are being developed by STC TM 3 and are not yet available.