NEC NDA-24233 manual Appendix C Isdn Q.931 Cause Code Definitions

VisuaLink 128/384 Engineering GuideAppendix 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.
		The route to the destination network is not recognized, either
2	No route to specified transit network	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.
		A call is being cleared because the B-channel is being preempted for
8	Preemption	a call of higher priority. If the preempted B-channel is not needed for
		the preempted call, it is released for prior use.
		A call is being cleared because the B-channel is being preempted for
9	Preempted - circuit reserved for reuse	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.
		Connection has not been established in the specified time period,
19	No answer from user (user alerted)	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.
		The number of the called party is no longer assigned: the new
22	Number changed	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	The user cannot be reached because the number is incomplete or in
	incomplete)	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.

NDA-24233 Issue 2 Page C-1