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Reference
3-20 GB1400 User Manual
LOCK Indicator and Actions Taken by the Analyzer if
Synchronization (Lock) is Lost
The LOCK LED indicates whether or not BER is above or below the current
synchronization threshold. The LOCK indicator will turn on while BER is below
the current synchronization threshold, and off while BER is above this threshold.
The setup actions taken by the Analyzer when BER crosses the synchronization
threshold will depend on the state of the AUTO SEARCH and DISABLE keys,
as shown in the table below.
Table 3-4. Actions Taken by Analyzer when Synchronization is Lost
AUTO SEARCH DISABLE Action when synchronization is lost (LOCK LED turns off)
on off Analyzer will attempt to find new pattern alignment, input level, input
delay, PRBS pattern and pattern polarity
off off Analyzer will attempt to find new pattern alignment.
off on
No setup change—Analyzer will continue to measure BER and count
errors.
on on (this combination not allowed)
AUTO SEARCH With PRBS Patterns
When using a PRBS pattern you can enable the AUTO SEARCH feature as
follows:
1. Set up the Generator to transmit a PRBS pattern.
2. Set up the Analyzer as follows:
EXT (ref. data input control), off
SYNC DISABLE, off
AUTO SEARCH, on
After you perform this procedure, the auto-search feature will be enabled and the
instrument will immediately attempt to re-synchronize with the received test
signal. Once lock is achieved—that is once BER goes below the synchronization
threshold—the BIT and PHASE history indicators will be cleared (turned off)
and all current error counts will be reset to zero. The SYNC LOSS indicator will
remain on, however, until cleared by the user.
NOTE: The AUTO SEARCH feature will work over a wide range of conditions.
Therefore if you have set up the Generator to generate a standard PRBS, enabled
the AUTO SEARCH feature on the Analyzer, but the Analyzer LOCK LED still
fails to turn on, then it is likely that a problem exists in the device under test or
your patch cord connections.