The system of clock network synchronization (CNS) of the Unified backbone digital communications network of OJSC “Russian Railways” was built in 1999 - 2002 in accordance with the general diagram of the CNS network developed jointly by the CJSC Company TransTeleCom, the Central Research Institute of Communications and federal state unitary enterprise “Giprotranssignalsvyaz.”

The system is implemented on the basis of equipment supplied by Russian (CJSC “Vremya-Ch”) and foreign manufacturers (“Symmetricom” firm), and includes:

  • primary reference synchronizers located in Moscow, St. Petersburg, Novosibirsk, Khabarovsk, Kaliningrad and Yuzhno-Sakhalinsk;
  • 45 secondary master synchronizers;
  • a certified system of CNS network management.

The CNS system is designed for the long-term future period; it is based on the most advanced technology solutions and provides a branched homogeneous network for generation, delivery, and distribution of clock signals applied to the SDH transport network.

Reliability and survivability of the CNS system is ensured by a homogeneous communications network, availability of direct ways of synchronization and additional signals from the GPS/GLONASS-receivers consisting of primary and secondary reference synchronizers, emergency use of a combined mode of CNS system operation by “master-slave” and “distributed primary reference synchronizer” hierarchies organized by the post-warranty service of vendor companies.

The system works with the basic CNS system of OJSC “Rostelecom” in pseudo synchronous mode, which in combination comprises the national system of clock network synchronization.

The CNS system of the unified DBN is certified in accordance with the requirements of RD 45.230-2001 “Audit of clock network synchronization systems.” The quality of synchronization signals corresponds with a production reserve to Recommendations ITU-T G.823, G.811, G.812, G.813 and standards requirements ETSI 300 462-3, 4-6, allowing the unified DBN of OJSC “Russian Railways” to interact with the general usage communications network and providing consumers with various desired signals of time and frequency in accordance with R 45.09-2001 “Connection of network operators to a core network of clock network synchronization” at any connection point and in any conditions.