ACS-160 Series & STL-160 Series T1 Multiplexer Installation & Operation 2 – Functional Description
Version 2.11, August 2011
2-10 Harris Corporation
Intraplex Products
modules do not hold channel module configuration information, the switchover from a backup DI-B
CM-5RB module to a primary one is fixed at two seconds.
Figure 2-7. Redundant CM-5RB Functions in Drop and Insert Multiplexer
2.1.4.2 Switch from Backup to Primary CM-5RB Module
In revert (RVRT) configuration, the backup CM-5RB module automatically reverts control back to the
primary CM-5RB module when it detects that a hardware failure has been corrected. If you have
selected a line failure (LOF, LOS, YEL, AIS) for a switching criterion, the configuration should be set to
non-revertant (NVRT) due to the switching mechanics. For example, if a yellow alarm is received and
a switch occurs, the primary CM-5RB module no longer reports a yellow alarm because the signals are
no longer coming into it. If the switching is set to revert (RVRT), the failure appears repaired to the
backup CM, and the backup switches control back to the primary CM. The primary CM once again
detects an alarm and another backup switch occurs. This cycling of the switch back and forth between
redundant CMs continues until the alarm condition is removed.
The non-revertant configuration should also be set if the switches for loss of frame (LOF) or loss of
signal (LOS) are activated (ON), also due to switching mechanics. The module adapter directs the T1
line signals to only one CM-5RB. If the backup CM-5RB module is active, it has the T1 line signal. The
primary CM-5RB module can never regain the line signal and therefore remains in a failed condition.
A switch is initiated 50ms after a report is received that meets the switching criteria. The total time for
switching from the primary CM to a backup CM (or vice versa) is less than 100 ms but results in a loss
of frame and signal during that period of time.
When reverting back to the primary, the backup CM must first transmit the channel module
configuration settings to the primary CM-5RB. While the backup CM is transmitting the configuration
settings, the front panel display reads “WAIT.” The transmission of the configuration settings can take
up to two minutes for a full shelf of 18 channel modules. When setting transmission is complete, the
“WAIT” display clears and the switchover is initiated (switchover appears to be instantaneous).
2.1.4.3 Module and Line Redundancy
Module and line redundancy features are available with these common modules:
● CM-5RB module for T1 systems
● CM-5RTD module for Time Delayed T1 systems
Notes: The CM-5R common module, an earlier version of the CM-5RB module, is the first generation
CM to combine line and module redundancy. The CM-5RB module should not be used in the
same equipment shelf as the CM-5R module.
Any combination of the CM-5RB module in a single equipment shelf with older version
common modules does not function properly (that is, a CM-5RB module cannot act as a
backup for a CM-5R or vice versa). To determine if a common module has combined module
and line redundancy capability, check the ejector tab. It has one of these labels: “CM-5RB,”
“CM-5R,” or “CM-5RTD.”
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