Avaya DEFINITY Server CSI Maintenance Manual page 1306

If a call is present, the Specification defines the permissible Call States as well.
There are tests in the Short and Long Test Sequences for DS1 ISDN Trunk
designed to audit these states and ensure agreement between both ends of the
PRI connection.
Alarming Based on Service States
A warning alarm is logged against a DS1 ISDN B-channel trunk when it is placed
in the Maintenance/Far-End or Out-Of-Service/Far-End states, during which the
trunk is unusable for outgoing calls. When a warning alarm is present, use status
trunk group#/member# command to determine the exact state. Other alarms
can be diagnosed by using the short and/or long test sequences. Note that an
ISDN B-channel trunk can be placed in a Far-End service state by either action
taken by the far-end switch or by failure of the far-end switch to respond. For
example, if the far-end does not respond to a Remote Layer 3 Query (Test #637
for ISDN-SGR), the associated DS1 ISDN trunk B-channels is placed in the
Maintenance/Far-End service state.
As a port on a DS1 circuit pack (DS1-BD or UDS1-BD), and as part of a signaling
group dependent on a D-channel (ISDN-PLK) for signaling, operation of the
ISDN-TRK is dependent on the health of these other maintenance objects.
DS1 ISDN Trunk Service States
This section defines the possible service states of a DS1 ISDN trunk, explains the
reason for each service state, and provides the recommended recovery
procedures (when required).
Service States
In-Service (INS)
The B-channel is in its normal operating state.
Out-of-Service/Far-end (OOS/FE)
A B-channel is initialized to this state when administered and it may also be
in this state if there is a failure on the B-channel attributed to a problem on
the far-end switch. The switch sends messages to the far-end to negotiate
the B-channel into service. If the far-end does not respond to the messages
within a certain time period, then the service state remains out-of-service
and maintenance will periodically resend the messages. The trunk is
unusable for outgoing calls. On US interfaces, the trunk is unusable for
incoming calls, but on non-US interfaces, incoming calls will be accepted.
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Issue 5 October 2002 555-233-119