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NDA-24233 Issue 2 Page C-1
VisuaLink 128/384 Engineering Guide Appendix C
Appendix C: ISDN Q.931 Cause Code Definitions
The following table defines the Q.931 cause codes that the VisuaLink 128/384
writes to event files. Q.931 specification defines the layer-3 protocol for two
connected ISDN devices.
Table C: ISDN Q.931 Cause Code Definitions
Code Meaning Explanation
1 Unallocated (unassigned) number
The requested destination can not be reached because the number
is not currently assigned.
2 No route to specified transit network
The route to the destination network is not recognized, either
because it does not exist or because it does not serve the equipment
sending the message.
3 No route to destination
The network through which the call has been routed does not serve
the desired destination.
8 Preemption
A call is being cleared because the B-channel is being preempted for
a call of higher priority. If the preempted B-channel is not needed for
the preempted call, it is released for prior use.
9 Preempted - circuit reserved for reuse
A call is being cleared because the B-channel is being preempted for
a call of higher priority. The B-channel is dedicated to the preempted
call.
16 Normal call clearing A call is being cleared at the request of one of the users.
17 User busy The user line is busy.
18 No user responding
No alert or connect indication was received within the prescribed
period of time.
19 No answer from user (user alerted)
Connection has not been established in the specified time period,
and an alert has been received. (Internal network timers may
generate this cause.)
21 Call rejected
The call was rejected despite the equipment being compatible and
not in use.
22 Number changed
The number of the called party is no longer assigned: the new
number may be reported in the message. Cause code 1 is assigned
if the network does not support this function.
27 Destination out of order
A signaling message could not be delivered to the user, indicating
that the interface to the destination is not functioning correctly.
28
Invalid number format (address
incomplete)
The user cannot be reached because the number is incomplete or in
the wrong format.
30 Response to STATUS ENQUIRY A message has been received in response to a STATUS ENQUIRY.
31 Normal, unspecified A normal event has occurred for which no other cause applies.
34 No circuit/channel available
No appropriate circuit or channel is currently available to handle the
call.
41 Temporary failure The network is temporarily not functioning correctly.
42 Switching equipment congestion The switching equipment is experiencing a period of high traffic.