ISDN Cause Codes (ERROR Codes) Cause codes [Q931] Code Cause 0 Valid cause code not yet received 1 Unallocated (unassigned) number 2 No route to specified transit network (WAN) 3 No route to destination 4 send special information tone 5 misdialled trunk prefix. 6 Channel unacceptable 7 Call awarded and being delivered in an established channel 8 Prefix 0 dialed but not allowed 9 Prefix 1 dialed but not allowed 10 Prefix 1 dialed but not required 11 More digits received than allowed, call is proceeding 16 Normal call clearing 17 User busy 18 No user responding 19 no answer from user 21 Call rejected 22 Number changed 23 Reverse charging rejected 24 Call suspended 25 Call resumed 26 Non-selected user clearing 27 Destination out of order 28 Invalid number format (incomplete number) 29 Facility rejected 30 Response to STATUS ENQUIRY 31 Normal, unspecified 33 Circuit out of order 34 No circuit/channel available 35 Destination unattainable 37 Degraded service 38 Network (WAN) out of order 39 Transit delay range cannot be achieved 40 Throughput range cannot be achieved 41 Temporary failure 42 Switching equipment congestion 43 Access information discarded 44 Requested circuit channel not available 45 Pre-empted 46 Precedence call blocked 47 Resource unavailable - unspecified 49 Quality of service unavailable 50 Requested facility not subscribed 51 Reverse charging not allowed 52 Outgoing calls barred 53 Outgoing calls barred within CUG 54 Incoming calls barred 55 Incoming calls barred within CUG 56 Call waiting not subscribed 57 Bearer capability not authorized 58 Bearer capability not presently available 63 Service or option not available, unspecified 65 Bearer service not implemented 66 Channel type not implemented 67 Transit network selection not implemented 68 Message not implemented 69 Requested facility not implemented 70 Only restricted digital information bearer capability is available 79 Service or option not implemented, unspecified 81 Invalid call reference value 82 Identified channel does not exist 83 A suspended call exists, but this call identity does not 84 Call identity in use 85 No call suspended 86 Call having the requested call identity has been cleared 87 Called user not member of CUG 88 Incompatible destination 89 Non-existent abbreviated address entry 90 Destination address missing, and direct call not subscribed 91 Invalid transit network selection (national use) 92 Invalid facility parameter 93 Mandatory information element is missing 95 Invalid message, unspecified 96 Mandatory information element is missing 97 Message type non-existent or not implemented 98 Message not compatible with call state or message type non-existent or not implemented 99 information element nonexistent or not implemented 100 Invalid information element contents 101 Message not compatible with call state 102 Recovery on timer expiry 103 parameter non-existent or not implemented - passed on 111 Protocol error unspecified 127 Internetworking, unspecified