The Asterisk hangup causes are delivered to the dialplan in the ${HANGUPCAUSE} channel variable after a call (after execution of "dial").

In SIP, we have a conversion table to convert between SIP return codes and Q.931 both ways. This is to improve SIP/ISDN compatibility.

These are the current codes, based on the Q.850/Q.931 specification:

- AST_CAUSE_UNALLOCATED                      1
- AST_CAUSE_NO_ROUTE_TRANSIT_NET             2
- AST_CAUSE_NO_ROUTE_DESTINATION             3
- AST_CAUSE_MISDIALLED_TRUNK_PREFIX          5
- AST_CAUSE_CHANNEL_UNACCEPTABLE             6
- AST_CAUSE_CALL_AWARDED_DELIVERED           7
- AST_CAUSE_PRE_EMPTED                       8
- AST_CAUSE_NUMBER_PORTED_NOT_HERE          14
- AST_CAUSE_NORMAL_CLEARING                 16
- AST_CAUSE_USER_BUSY                       17
- AST_CAUSE_NO_USER_RESPONSE                18
- AST_CAUSE_NO_ANSWER                       19
- AST_CAUSE_CALL_REJECTED                   21
- AST_CAUSE_NUMBER_CHANGED                  22
- AST_CAUSE_REDIRECTED_TO_NEW_DESTINATION   23
- AST_CAUSE_ANSWERED_ELSEWHERE              26
- AST_CAUSE_DESTINATION_OUT_OF_ORDER        27
- AST_CAUSE_INVALID_NUMBER_FORMAT           28
- AST_CAUSE_FACILITY_REJECTED               29
- AST_CAUSE_RESPONSE_TO_STATUS_ENQUIRY      30
- AST_CAUSE_NORMAL_UNSPECIFIED              31
- AST_CAUSE_NORMAL_CIRCUIT_CONGESTION       34
- AST_CAUSE_NETWORK_OUT_OF_ORDER            38
- AST_CAUSE_NORMAL_TEMPORARY_FAILURE        41
- AST_CAUSE_SWITCH_CONGESTION               42
- AST_CAUSE_ACCESS_INFO_DISCARDED           43
- AST_CAUSE_REQUESTED_CHAN_UNAVAIL          44
- AST_CAUSE_FACILITY_NOT_SUBSCRIBED         50
- AST_CAUSE_OUTGOING_CALL_BARRED            52
- AST_CAUSE_INCOMING_CALL_BARRED            54
- AST_CAUSE_BEARERCAPABILITY_NOTAUTH        57
- AST_CAUSE_BEARERCAPABILITY_NOTAVAIL       58
- AST_CAUSE_BEARERCAPABILITY_NOTIMPL        65
- AST_CAUSE_CHAN_NOT_IMPLEMENTED            66
- AST_CAUSE_FACILITY_NOT_IMPLEMENTED        69
- AST_CAUSE_INVALID_CALL_REFERENCE          81
- AST_CAUSE_INCOMPATIBLE_DESTINATION        88
- AST_CAUSE_INVALID_MSG_UNSPECIFIED         95
- AST_CAUSE_MANDATORY_IE_MISSING            96
- AST_CAUSE_MESSAGE_TYPE_NONEXIST           97
- AST_CAUSE_WRONG_MESSAGE                   98
- AST_CAUSE_IE_NONEXIST                     99
- AST_CAUSE_INVALID_IE_CONTENTS            100
- AST_CAUSE_WRONG_CALL_STATE               101
- AST_CAUSE_RECOVERY_ON_TIMER_EXPIRE       102
- AST_CAUSE_MANDATORY_IE_LENGTH_ERROR      103
- AST_CAUSE_PROTOCOL_ERROR                 111
- AST_CAUSE_INTERWORKING                   127

For more information:

app_dial.c