User manual

Wide Bank 28 DS3 - Release 2.4 July 2004 2-27
Product Description
Low-Speed (LS) Redundancy
Restoring to Original Status (Revertive Switching)
Because some circuit failures can look like line failures (LOS or Major LCV), the Wide Bank
provides a revertive switching feature to keep spares available for use by other circuits.
When a line failure occurs, the Wide Bank will move the channel to the spare circuit. If the failure
remains, the problem is a line failure, so the channel is moved back to the home circuit. However,
if the failure clears on the spare circuit, the next action depends on the revertive ds1 setting.
Revertive Off – the channel will remain on the spare circuit until you replace the home card or
manually move the channel back to the home circuit.
Revertive On – a self-test will be performed on the home circuit and one of the following actions
will occur:
 Self-Test Fails – the channel will remain on the spare circuit until you replace the home card
or manually move the channel back to the home circuit.
 Self-Test Passes – the channel will be moved home after 2 minutes. However, if three failures
occur within a 24-hour period, the low-speed circuit will be locked out and will remain on the
spare card. If fewer than three failures occur on the same circuit within 24 hours, the failure
count will decrement by 1 each day until the count is again zero. If desired, you can reset the
locked-out circuit (revertive ds1 reset), which will move the channel back to the home circuit.
Hot-Swapping a Failed Standard Low-Speed Card
CAUTION! THIS PROCEDURE CAN CAUSE DROPPED CALLS ON THE LOW-SPEED
CIRCUITS THAT HAVE BEEN SWITCHED OVER BY AUTOMATIC ELECTRONIC REDUNDANCY.
A standard (non-MSO) low-speed card that causes a switchover can be hot-swapped (swapped with
power on) but any calls on the circuits to the failed card, including those that were switched to the
spare low-speed card, will be dropped. The circuits will become active again as soon as the new
card has completed self-tests, and the previously switched failing channel will be switched back to
the new card. The spare card circuit is now unused and available.
Hot-Swapping a Failed MSO Low-Speed Card
The Maintenance Service Option (MSO) low-speed card consists of two separating portions, the
MSO Relay card and the MSO Electronics card. The MSO low-speed card allows the failed DS1 or
E1 Electronic circuits of that card to be replaced while the MSO Relay portion automatically
maintains service on the spare low-speed card. Once a new MSO Electronics card is inserted and
passes self-test, the circuits currently on the spare card are automatically switched back to the
“home” circuit.
Priority of service on the spare low-speed card is always given to those DS1 or E1 circuits from the
first MSO Electronics card removed from the system. Because removing an MSO Electronics card
requires four spare DS1 circuits (three E1) to be available, only one MSO card can be removed at
a time (see Low-Speed (LS) Redundancy on page 2-22). If any of the spares are already in use by