Symmetricom SDU-2000, User Manual

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Clock Module Reference Data
Stratum 2E Clock Module
124 SSU-2000 User’s Guide 12713020-002-2 Revision D – April 2004
Stratum 2E Clock Module
This section provides user reference information for the Stratum 2E Clock module
(part number 23413016-000-0) used in the SSU-2000.
Functional Overview
The Stratum 2E Clock module uses a Rubidium oscillator and meets or exceeds the
performance requirements for ITU and ETSI Type I Transit and Type II Local Node
clocks and ANSI and Telcordia Technologies (Bellcore) Stratum 2 clocks.
The Clock module reads measurement data from the Input modules, provides
frequency control of the oscillators through DDS circuitry, and generates reference
signals used by the input and Output modules.
A typical SSU-2000 system contains dual redundant Clock modules. Each Clock
module maintains phase synchronization with the redundant Clock module. Its
hardware and software also provides for temperature compensation, an initial offset
adjustment, and frequency adjustment resolution of 1 x 10-13 or better.
With redundant Clock modules, one is selected as the master and the other as
backup, with automatic switching on module removal or failure.
The master Clock module controls the operation of the Input and Output modules
and downloads module configuration information to all modules (except for the
Communications module), requests measurement data and status from the Input
modules, and sets the Output modules to use currently selected clock signals. The
Clock modules maintain an internal time-of-day clock that is used to time stamp
events to within 0.1 second of detection of the event.
This module provides an 8 kHz signal used by the Input modules and a 4 kHz signal
used by the Output modules. Each Clock module provides one set of signals for use
by the modules in the main chassis, and a separate set for the expansion shelves.