Overview
When reviewing fax failures you may sometimes see ISDN cause codes, if using an ISDN device, and require an interpretation of what that code actually means. They could be called reason codes, cause codes or just error codes. This article provides a list of ISDN disconnect cause codes.
Information
Below is a list of ISDN disconnect cause codes including their hex and decimal numeric values.
| Hex | Decimal | Cause |
|---|---|---|
| 0x1 | 1 | Unallocated or unassigned number |
| 0x2 | 2 | No route to a specified transit network (Transit Network Identity) |
| 0x3 | 3 | No route to the destination |
| 0x4 | 4 | Send special information tone |
| 0x5 | 5 | Misdialled trunk prefix |
| 0x6 | 6 | Channel unacceptable |
| 0x7 | 7 | Call awarded and being delivered in an established channel |
| 0x8 | 8 | Prefix 0 dialed but not allowed |
| 0x9 | 9 | Prefix 1 dialed but not allowed |
| 0xA | 10 | Prefix 1 not dialed but required |
| 0xB | 11 | More digits received than allowed, the call is proceeding |
| 0x10 | 16 | Normal call clearing |
| 0x11 | 17 | User busy |
| 0x12 | 18 | No user responding |
| 0x13 | 19 | T.301 expired: - User Alerted, No answer from the user |
| 0x15 | 21 | Call rejected |
| 0x16 | 22 | Number changed to number in the diagnostic field. |
| 0x17 | 23 | Reverse charging rejected |
| 0x18 | 24 | Call suspended |
| 0x19 | 25 | Call resumed |
| 0x1A | 26 | Non-selected user clearing |
| 0x1B | 27 | Destination out of order |
| 0x1C | 28 | Invalid number format or incomplete address |
| 0x1D | 29 | EKTS facility rejected by network |
| 0x1E | 30 | Response to STATUS ENQUIRY |
| 0x1F | 31 | Normal, unspecified |
| 0x21 | 33 | Circuit out of order |
| 0x22 | 34 | No circuit/channel available |
| 0x23 | 35 | Destination unattainable |
| 0x24 | 36 | Out of order |
| 0x25 | 37 | Degraded service |
| 0x26 | 38 | Network out of order |
| 0x27 | 39 | Transit delay range cannot be achieved |
| 0x28 | 40 | Throughput range cannot be achieved |
| 0x29 | 41 | Temporary failure |
| 0x2A | 42 | Switching equipment congestion |
| 0x2B | 43 | Access information discarded |
| 0x2C | 44 | Requested circuit channel not available |
| 0x2D | 45 | Preempted |
| 0x2E | 46 | Precedence call blocked |
| 0x2F | 47 | Resource unavailable, unspecified |
| 0x31 | 49 | Quality of service unavailable |
| 0x32 | 50 | Requested facility not subscribed |
| 0x33 | 51 | Reverse charging not allowed |
| 0x34 | 52 | Outgoing calls barred |
| 0x35 | 53 | Outgoing calls barred within CUG |
| 0x36 | 54 | Incoming calls barred |
| 0x37 | 55 | Incoming calls barred within CUG |
| 0x38 | 56 | Call waiting not subscribed |
| 0x39 | 57 | Bearer capability not authorized |
| 0x3A | 58 | Bearer capability not presently available |
| 0x3F | 63 | Service or option not available, unspecified |
| 0x41 | 65 | Bearer service not implemented |
| 0x42 | 66 | Channel type not implemented |
| 0x43 | 67 | Transit network selection not implemented |
| 0x44 | 68 | Message not implemented |
| 0x45 | 69 | Requested facility not implemented |
| 0x46 | 70 | Only restricted digital information bearer capability is available |
| 0x4F | 79 | Service or option not implemented, unspecified |
| 0x51 | 81 | Invalid call reference value |
| 0x52 | 82 | Identified channel does not exist |
| 0x53 | 83 | A suspended call exists, but this call identity does not |
| 0x54 | 84 | Call identity in use |
| 0x55 | 85 | No call suspended |
| 0x56 | 86 | Call having the requested call identity has been cleared |
| 0x57 | 87 | Called user not member of CUG |
| 0x58 | 88 | Incompatible destination |
| 0x59 | 89 | Non-existent abbreviated address entry |
| 0x5A | 90 | Destination address missing, and direct call not subscribed |
| 0x5B | 91 | Invalid transit network selection (national use) |
| 0x5C | 92 | Invalid facility parameter 93 Mandatory information element is missing |
| 0x5D | 93 | Message type non-existent or not implemented |
| 0x5F | 95 | Invalid message, unspecified |
| 0x60 | 96 | Mandatory information element is missing |
| 0x61 | 97 | Message type non-existent or not implemented |
| 0x62 | 98 | Message not compatible with call state or message type non-existent or not implemented |
| 0x63 | 99 | Information element nonexistent or not implemented |
| 0x64 | 100 | Invalid information element contents |
| 0x65 | 101 | Message not compatible with call state |
| 0x66 | 102 | Recovery on timer expiry |
| 0x67 | 103 | Parameter non-existent or not implemented - passed on |
| 0x6F | 111 | Protocol error, unspecified |
| 0x7F | 127 | Internetworking, unspecified |
| 0x80+ | 128 or
higher |
Proprietary diagnostic code (not necessarily bad). Typically used to pass proprietary control or maintenance messages between multiplexers. |