5700MSC-IP
IP Network Grand Master Clock & Video Master Clock System
Revision 0.2 Page - 75
5.3.1.2. Configuring the Genlock Capture Range
The Genlock Range menu item is used to select the type of oscillator to
use when locking to video or 5/10MHz references.
Set this to Narrow
to use the ovenized oscillator when the frequency
stability of the reference is tightly controlled and within ±0.1 ppm. The
ovenized oscillator provides excellent stability and enables use of the Slow
lock mode. The Slow lock mode allows the 5700MSC-IP
smoothly from a loss of reference or reference shift condition. The Narrow
range is superior to the Wide range in every way except in lock time and
lock range. It is the default setting and does not normally need to be
changed.
Select the Wide
range only when a wide locking range of ±15ppm is
required and when very fast lock times are needed. This may be required
in some post-production facilities where the input reference is changing
occasionally and a fast relock time is desired. Low freerun stability and
slightly higher jitter are the drawbacks of the wide range.
5.3.1.3. Selecting the Frequency Reference Lock Type
The Lock Type menu item is used to select how the 5700MSC-IP will relock
to its frequency reference when the reference is lost and then regained, or
experiences a change.
In Abrupt mode, whenever the 5700MSC-IP
detects that its internal
oscillator is no longer synchronized to the reference it will make a sudden
change to bring it back into lock. This may cause disturbances to the
outputs as the unit shifts its frequency and phase.
In Slow mode, when the 5700MSC-IP detects that its internal oscillator is
not synchronized to the reference it will report REF JAM NEEDED on the
LCD display and optionally send an SNMP trap. The unit will then slowly
adjust its internal oscillator to bring it back into lock with the reference. This
gradual correction will not cause any disturbances to the outputs as they re-
phase. This adjustment may take a long time, depending on the size of the
discrepancy between the internal oscillator and reference. If the unit is
required to lock to its reference without delay the user can perform a manual
jam by selecting the Jam Input menu item. The Slow
lock type is only
available if the Genlock Range is set to Narrow.
If a large shift in the reference occurs while Slow lock mode is enabled, the outputs
of the 5700MSC-IP may be out of phase for a long time while relocking. The
5700MSC-IP will gradually slew its oscillator to bring it back into phase with the
reference. This slewing action combined with the phase shift may seem to indicate
that the unit is completely unlocked to the reference. This is not a fault and a manual
jam can be performed to force the 5700MSC-IP to lock immediately.
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