Input Signal Faults; Priority Level - Symmetricom TSG-3800 Series User Manual

Operating the TSG-3800
Selecting the Input Reference Signal

Input Signal Faults

The input signal and measurement data is checked for errors each second. If no
errors are found, the input is considered valid and may be selected as the reference
input. Loss of Signal (LOS), Alarm Indication Signal (AIS), Bi-Polar Violations
(BPV), Cyclic Redundancy Check (CRC) errors, and Out of Frame (OOF)
occurrences can be used to disqualify an input signal for use as a reference. Timers
are used for each of these occurrences, where the number of seconds before an
input fails and for the number of error-free seconds required before the input is
qualified. Table 3-6 lists the timer ranges and default values for input errors, as well
as the default alarm condition.
When the error timer is exceeded, the fault condition can be set to FAIL the input,
generate an ALARM but not FAIL the input, REPORT the condition only, or IGNORE
the condition. LOS and AIS are set to FAIL, and BPV, OOF, and CRC are set to
ALARM by default.
Detecting Input Errors, on page 330, describes how to display and to set the timer
ranges and the alarm conditions for each of the input signal errors.
Maximum Time Interval Errors (MTIE) and Frequency errors may also cause input
signal faults when exceeding the set thresholds, set in nanoseconds. There are two
limits, L1 and L2, for each condition at 100, 1000, and 10000 Second time periods
which may be set to the FAIL, ALARM, REPORT, or IGNORE mode. When a FAIL
limit has been exceeded on an input, it is no longer valid for use as a reference
signal. Limit (L1) for both, MTIE and FREQ, is set to FAIL and Limit 2 (L2) is set to
ALARM by default. Setting these limits too small may cause all inputs to fail, placing
the unit in Holdover mode.
Provisioning MTIE and Frequency Parameters, on page 334, describes how to
display and to set the alarm limits for MTIE and FREQ errors.

Priority Level

The TSG-3800 never selects a failed input as a reference. The provisioned Priority
level assigned to each input port controls selection of valid input signals. The
assigned priority ranges from 1 (highest) to 4 (lowest), or 0 for monitor only. The
priorities default to the module slot number for port 1, with ports 2 and 3 of the
3-Port modules set to Monitor. A module port may also be disabled so that no
alarms or events are reported for that input and no data is collected. An input set to
Monitor continues to collect and store data, generate alarms or reports (depending
on fault setting), but it cannot be selected as a reference signal.
A set threshold of zero in both the MTIE and Frequency limit settings disables the
alarm limit (sets it to ignore).
For information on the syntax for provisioning the Priority level, refer to Input
Command, on page 350.
12778474-002-2 Revision F – March 2004 TSG-3800 User's Guide 83
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