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Product Overview
2.3.5
Pass-through
In case of failure or extraction of internal oscillators (THC cards), the equipment will
automatically activate its “pass-through” (Clock bypass) function when at least one
input signal 2.048MHz, E1 or GPS is connected and qualified.
It is an autonomous option of 'last-resort' in SSU input selection upon critical internal
failure to prevent prolonged outage.
The selected input signal is directly connected to the Signal Generator Cards (SGC)
allowing all Output Cards to generate synchronization signals.
The output signal quality will be, in this “pass-through” operating mode, the same as
the selected input signal (no filtering and jitter attenuation).
Note:
Upon switching to the pass-through mode, the output signal can be
affected with a phase jump as the THC will not be there to filter and
insure phase alignment.
Note:
For more details and configuration, refer to section 6.8.6
2.3.6
Performance Measurement
The OSA 5548C SSU monitors, measures and calculates performances in Ym
(fractional frequency), TDEV (Time DEViation) and MTIE (Maximum Time Interval
Error) of every single input signal connected to its inputs, as well as the GPS input
line.
The measurement is performed in the INC cards, which compare the input signal
against a reliable frequency reference produced by the signal filtered and processed
by the active THC card.
The performance measurement is processed when the input line meets one of the
following criteria:


Enabled: the line is activated to select an input reference.
Monitored: the input line is only measured in order to assess the signal.
The user can also define a performance threshold to disqualify and reject input
signals that fail to meet this programmable threshold.
OSA 5548C SSU-E60 - User Manual - Revision P - October 2013
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