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 specif ication defines the layer-3 pr ot ocol for two

connected ISDN devices.

Table C: ISDN Q.931 Cause Code Definitions
Code Meaning Explanation
1Unallocated (unassigned) number The requested destination can not be reached becaus e the number
is not currently assigned.
2No 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 equipme nt
sending the message.
3No route to destination The network through which the call has been routed does not serv e
the desired destination.
8Preemption A call is being cleared because the B-channe l is being preem pted for
a call of higher priority. If the preempted B-channel is not need ed for
the preempted call, it is released for prior use.
9Preempted - circuit reserved for reuse A call is being cleared because the B-cha nnel is being pre empted for
a call of higher priority. The B-channe l 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 equipmen t 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 assign ed
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 inc omplete or in
the wrong format.
30 Response to STATUS ENQUIRY A message has been received in response to a STATUS ENQU IRY.
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 corr ectly.
42 Switching equipment congestion The switching equipment is experiencing a period of high traffic.