Symmetricom SDU-2000, User Manual

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12713020-002-2 Revision D – April 2004 SSU-2000 User’s Guide 147
Input Module Reference Data
1-Port and 3-Port E1 Input Modules
TDEV Calculation
The Input module automatically (without user intervention) calculates TDEV (the
measurement of the frequency components in a series of phase readings) for all its
inputs and reports on the past 24 hours of TDEV history. TDEV is retrieved on hour
boundaries, though the stop time used may be current time.
Reported time periods include: 0.05, 0.10, 0.30, 0.60, 1.0, 2.0, 3.0, 6.0, 10.0, 30.0,
60.0, 100.0, 300.0, 600.0, 1000.0, 3000.0, 6000.0, and 10000.0 seconds
The E1 Input module also contains provisions for zeroing the phase readings for
one channel in response to a command from the Communications module. Once
the phase is zeroed, all subsequent phase measurements are expressed in terms of
how much they differ from the reading at the time the phase was zeroed.
Zeroing the phase invalidates all past phase averages, TDEV, and MTIE.
Sync Status Messages
The E1 Input module reads and processes Sync Status Messages (in accordance
with specification ITU-T Composite Clock (CC) for E1 signals), to determine the
traceability of inputs. This traceability information is then used by the Clock modules
in selecting a reference signal and embedded into the system’s outputs. For E1
inputs, an SSM is valid if three consecutive matching SSMs are received.
SSM Selection Criteria
If the E1 Input module is configured for provisioned mode, it will use the provisioned
SSM. If configured for automatic mode, the Input module uses the most recent valid
SSM. If a valid SSM is not received, the module uses the provisioned SSM. Refer to
DS1 and E1 Input Module Default Settings , on page 424, for more information on
provisioning SSMs.
E1 Input Module Alarm Modes
The E1 Input module responds to various alarm conditions according to user-set
alarm levels. Each level is associated with a set of actions as follows:
Table 7-1. E1 Input Module Alarm Modes
Alarm Mode Action Alarm Elevation
IGNORE Do nothing Cannot be elevated to a higher severity level
REPORT Do nothing Cannot be elevated to a higher severity level
MINOR Generate event message Elevate to Major if the alarm condition persists
beyond the user-set elevation time limit
MAJOR Generate event message Elevate to Critical if the alarm condition persists
beyond the user-set elevation time limit
CRITICAL Generate event message
Fault Port
Cannot be elevated to a higher severity level