Symmetricom SDU-2000, User Manual

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Product Overview
System Architecture
30 SSU-2000 User’s Guide 12713020-002-2 Revision D – April 2004
As indicated in Figure 1-5 , the SSU-2000 consists of four major sections:
Input section
Clock section
Output section
Communications section
Input Section
The input section consists of one to nine Input modules to which you connect
reference signals that are tested for signal integrity; the Input modules are
described in
Chapter 7, Input Module Reference Data . You provision each input
using the ICS INPUT and REF commands or the TL1 SET-PRMTR-INPUT and
SET-INPUT-REF commands.
The Input modules measure the phase between the input signal and the clock
oscillator(s). From these phase measurements, the DS1/E1 Input modules compute
frequency offset and wander of the input signals. Wander is reported in terms of
Maximum Time Interval Error (MTIE) and Time Deviation (TDEV). The data is then
stored for use in the SSU-2000 and reported through the Communications module.
You can install one or two GPS Input modules that use the satellite-based Global
Positioning System signals as a synchronization reference.The Input signal types
supported are:
DS1/Clock (unframed)
E1/Clock (unframed)
GPS
Composite Clock
Selecting the Input
Many factors influence which input reference the SSU-2000 uses:
Priority
PQL/SSM
Switching mode
User-assigned Input State
Active alarms on an input
You can provision the SSU-2000 to automatically select the highest-quality input
signal, or you can manually select the input signal you want to use. Two factors
determine the quality of the input: the user-defined Priority level, and the PQL/ SSM.
These factors are used to determine which input is used, and what happens if that
input becomes disqualified.