Communications System Owner Manual
Table Of Contents
- Table of Contents
- ABOUT THIS DOCUMENT
- 1. INTRODUCTION TO CONNECTIVITY
- 2. COMMUNICATION SYSTEM NETWORKING (em AN OVERVIEW
- 3. TANDEM TIE TRUNK NETWORKS
- 4. MAIN-SATELLITE/TRIBUTARY (MS/T) NETWORKS THROUGH THE UDP OR MULTIPREMISES PACKAGES
- 5. ELECTRONIC TANDEM NETWORK (ETN) THROUGH THE ETN AND PNA PACKAGES
- 6. DISTRIBUTED COMMUNICATIONS SYSTEM (DCS)
- 7. DATA CONNECTIVITY - AN OVERVIEW
- 8. DATA COMMUNICATIONS CAPABILITIES
- 9. DATA COMMUNICATIONS CONFIGURATIONS
- A. RELATED DOCUMENTS
- B. SYNCHRONIZATION OF DIGITAL FACILITIES
- THE NEED FOR SYNCHRONIZATION
- SYNCHRONIZATION HIERARCHY
- CHANGES TO THE SCS SOFTWARE MADE AVAILABLE VIA SOFTWARE PATCHES
- NETWORK SYNCHRONIZATION AND ENGIINEERING
- AVAILABILITY OF SYNCHRONIZATION SOURCES
- CONCLUSIONS ON SYNCHRONIZATION
- USE OF GENERIC 2 AS A SYSTEM CLOCK REFERENCE
- USE OF GENERIC 1 AS A SYSTEM CLOCK REFERENCE
- C. TRUNKING TERMS AND CAPABILITIES
- D. COMMUNICATIONS PROTOCOLS
- E. LEAD DEFINITIONS
- F. NETWORKING FEATURES - AVAILABILITY MATRIX
- ABBREVIATIONS
- GLOSSARY
- INDEX
SYNCHRONIZATION OF DIGITAL FACILITIES B-27
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SECONDARY (BACKUP) FREQUENCY REFERENCE
DIGITAL TRANSMISSION FACILITY
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PRIMARY FREQUENCY REFERENCE
Figure B-20. Minimized Synchronization from One Node
External-Reference Selection Rules
There are seven rules for selecting external synchronization references. These rules are described next.
RULE 1:
Nodes within the externally referenced sublevel may not use as a reference source a facility from a node
within the internally referenced sublevel (refer to figure B-11, External and Internal Reference Levels, for
an explanation of these terms).
RULES 2 THROUGH 7:
Rules 2 through 7 are the same for both internal- (that is, SCS, external stratum-3 clock, and HAC) and
external-reference selections.