12713020-002-2 Revision D – April 2004 SSU-2000 User’s Guide 51
Product Overview
Overview of SSU-2000 Operation
Overview of SSU-2000 Operation
After initial installation and configuration is completed, the SSU-2000 is capable of
unattended operation. After power-up, where the external power supplies are turned
on so that they supply power to the main shelf, the SSU-2000 performs a
self-diagnostic test routine and properly initializes the hardware. Any active Alarms
are time tagged and reported as Events. All Events are time tagged and the last 500
Events are stored in NVRAM. All Events can be remotely accessed and cleared by
a user with the appropriate security level. Several optional levels of password
protection are available for system protection as described in Overview of the
SSU-2000 Security System, on page 98.
After the internal oscillators on any installed Clock modules have warmed up, the
SSU-2000 enters the ACQUIRE mode to phase lock the oscillators to the external
references. After the SSU-2000 reaches the LOCKED mode on at least one of the
Clock modules, any change of state is reported as an Event.
Synchronization Status Messages (SSMs)
The SSU-2000 supports input and output SSMs. SSMs provide a method for
providing clock quality information to any equipment that uses synchronization
inputs. Table 1-3 describes the ANSI SSM values and the traceability associated
with each value. Table 1-4 describes the ITU SSM values and the traceability
associated with each value.
Table 1-3. ANSI SSM Quality Level Definitions
Description
Quality
Level
Abbreviation
Stratum 1 Traceable 1 PRS
Synchronized – traceability unknown 2 STU | UNK
Stratum 2 traceable 3 ST2
Transit Node traceable 4 TNC | TYPE I
Stratum 3E traceable 5 ST3E | TYPE III
Stratum 3 traceable 6 ST3 | TYPE IV
SONET Minimum Clock traceable
(20 ppm clock)
7SMC
Stratum 4 traceable 8 ST4
Do Not Use for synchronization 9 DUS
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