Specifications

is to allow the new Maintenance Module to
automatically ARM. This can occur in most
cases after some initial setup, as described
below.
2. Insert the new Maintenance Module.
When you insert the new Maintenance
Module, one of several things could occur,
based on the saved configuration. You should
check the status LEDs approximately five
seconds after power has been restored to the
newly inserted Maintenance Module. If the
ARMed led is ON, the setup criteria has
already been met, and the following steps may
not be necessary. Note, however, that you may
still need to configure the DS0 channel
assignments and/or the channel module
settings. The correct setting of the loop defin-
ition and the correct neighbors’ addresses for
the corresponding loop definition are the
primary items which allow the automatic
arming sequence to occur.
3. Unlock the chassis.
Before you perform any setup, the chassis
must be unlocked.
4. Perform the normal setup for a new
Maintenance Module.
You can accomplish this either by down-
loading a previously saved configuration or
by manually configuring the DS0 channel
assignments and the channel modules.
5. Perform the APM “Define” procedure.
To do this, use the “APM Define” command.
When the “APM Loop Definition” dialog box
comes up, enter the correct neighbor
addresses and select the appropriate loop defi-
nition. After successfully downloading these
configuration items, check the status LEDs. If
the ARMed LED is on, the node successfully
performed the automatic arming function.
Also, a system target, “APM Loop 1
Automatically ARMed,” will be logged in the
event buffer.
If the automatic ARM did not occur, check the
status of APM with FCS using the “APM Status”
command.
Table 5-3 describes APM states and provides
explanations of why APM did NOT ARM auto-
matically.
5.1.4 APM Application Notes
5.1.4.1 Pre-configured pass-through
No pass-through connections should be made in
the DS0 Channel assignments map unless they are
required for the operation of channel modules on
the primary path. This will cause an incorrect
alternate path if a break occurs adjacent to the
unused pass-through.
5.1.4.2 Re-using Channels on a loop
For APM to work correctly, all channels must be
reserved around the loop for each channel in the
primary path. For example: If channel 2 is being
used for point-to-point communications for
HCBs, channel 2 should not be used for any other
communication on ANY other node on the entire
loop. Channels which need to be re-used should
be skipped by alternate path mode. It is the user’s
responsibility to verify that the appropriate
channels are being skipped prior to “arming”
the loop.
5.1.4.3 Alternate Path Mode when No
Channels are Re-routed
When a loop is ARMed, the following items cause
the loop to go into Alternate Path Mode:
December 2008 Page 5–5
Chapter 5. Alternate Path Mode (APM)
5
State Define Arm Disarm
ARMed No Yes Yes
Down No No Yes
Flipped No No Yes
Inactive Yes No No
Ready for Yes Yes No
Arm
Table 5–2. APM Status Matrix.