9500 MXC User Manual
3DB 23063 ADAA - Rev 004 July 2007 Vol. VI-A-25
go before the ring will unwrap. Applies to both the Error-free Timer and Delay
Ring Unwrap Timer. (Counts down to zero)
Checking Wrap and Unwrap Operation
To simulate a ring radio-link failure:
• A Tx mute can be invoked in Diagnostics > System Controls, for the east or
west RAC.
• The east or west RAC can be withdrawn from its backplane.
To check for correct wrap operation:
1. First ensure the ring is operating normally, specifically that it is not already in
a wrapped state. This can be checked by quick inspection of the CT status bar.
2. Apply a BER test on a looped trib circuit, and confirm error-free operation.
3. Apply a Tx mute on the East RAC, or withdraw the RAC from its backplane,
and check for:
• Continuing error-free BER indication, after a momentary error blink.
• An errored second count of not more than two seconds (it will be one or two,
depending on the where errors begin and stop within the errored-second
count.
4. Remove the Tx mute (or return RAC to its backplane). Within several
seconds, normal link operation will be confirmed by a green RAC status LED
and an unlit RAC online LED. At this point the error-free timer is initiated,
and providing no further errors are detected on the link, the ring will revert to
normal unwrapped operation on time-out of the error-free timer setting.
• While the link is subject to the timer the online LED remains unlit.
• The online LED becomes green as soon as the ring link is unwrapped (traffic
is restored on the link).
• The time to go before an unwrap occurs is displayed by the RING unwrap
timer in the System/Controls screen.
Check that:
• Revertive switching occurs at time-out of the unwrap timer setting, once
normal link operation is restored.
• An error-free BER indication is maintained throughout, except for a
momentary error blink during the revertive switch (unwrap).
To avoid a power spike causing momentary errors on all node traffic, the ODU
cable must not be disconnected or reconnected on an operational RAC. Before
connection/disconnection, first withdraw a RAC from its backplane.
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