F73 – Alarm Control / Status
Status: Locked or Unlocked
The LPN (Low Phase Noise) PLL indicator reports “Locked” during normal operation
while the LPN oscillator on an LPN Card is locked to the XL-GPS’s internal oscillator.
The LPN PLL indicator reports “Unlocked” for several minutes after the unit is started
while the LPN oscillator on the card warms up. This is not a significant error, and if
needed, can be prevented by extending the duration of the Power-On Alarm Suppress.
If the LPN PLL indicator reports “Unlocked” at any time other than the warm-up period,
the LPN card’s PLL has failed or the LPN card’s oscillator can no longer be steered to the
internal XL-GPS oscillator. All outputs from the LPN card are unreliable and should not be
used. Contact Symmetricom Global Customer Assistance.
GPS
Locked: The GPS receiver is receiving a sufficient number of valid GPS satellite signals and
is generating a valid timing solution.
Unlocked: The GPS receiver is not providing a valid timing solution due to one of the
following causes:
• Insufficient visibility of GPS satellites at the antenna location.
• Poor GPS satellite signal strength
• A poorly positioned GPS antenna
• A broken or disconnected antenna cable
• An absent or non-functioning GPS receiver card
See “Installing the GPS Antenna” on page21 for GPS antenna installation guidelines.
IRIG
Status: OK or Fault
The IRIG indicator reports “OK” when an IRIG input on J1 is providing valid time. It
reports a “Fault” if one of the following is true:
n The time code signal isn’t connected to J1 on the main CPU card.
n F110 isn’t configured correctly for a given time code format or impedance con-
figuration.
n There is a high signal-to-noise ratio in the AM code.
n The DC level shift code level is inadequate or has too much jitter.
To solve a fault from the IRIG indicator, check that the preceding items are configured/set
up correctly.
DAC
098-00116-000 Rev. A............................... Page 97 of 221
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