Symmetricom SDU-2000, User Manual

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Product Overview
Typical System Configurations
28 SSU-2000 User’s Guide 12713020-002-2 Revision D – April 2004
Primary Reference Source (PRS) Configuration
In a Primary Reference Source (PRS) configuration ( Figure 1-3 ), the SSU-2000
meets the specifications defined in American National Standards Institute (ANSI)
T1.101-1999. ANSI defines a Primary Reference Source as “equipment that
provides a timing signal whose long term accuracy is maintained at 1x10
-11
or
better, with verification to Universal Coordinated Time (UTC), and whose timing
signal may be used as the basis of reference for the control of other clocks within a
network”. If standard Input modules are installed in the remaining input slots, this
configuration also allows for monitoring of up to 24 external signals, such as DS1,
E1, composite clock, and various clock frequencies. Time-of-day functionality is
available through an Ethernet port employing NTP.
Figure 1-3. SSU-2000 Configured as a Primary Reference Source
SSU-2000 Configured as a Monitor-Only System
The SSU-2000 can also be configured as a monitor-only system ( Figure 1-4 ) in
which one of the inputs is designated as the reference, and a clock module is locked
directly to this signal. The remaining input signals are then compared to the
phase-locked oscillators (and indirectly to the designated input reference).
The SSU-2000 continuously monitors the integrity of the incoming timing signal.
The operator defines input acceptance criteria and sets parameters for alarming.
When the incoming signal is acceptable (within the performance limits set by the
operator), the SSU-2000 phase-locks to the signal on a priority basis.
Figure 1-4. SSU-2000 Configured as a Monitor-Only System