| 1 | Unallocated number |
| 2 | No route to specified transit network |
| 3 | No route to destination |
| 6 | Channel unacceptable |
| 7 | Call awarded and being delivered in an established channel |
| 16 | Normal call clearing |
| 17 | User busy |
| 18 | No user responding |
| 19 | No answer from user (user alerted) |
| 21 | Call rejected |
| 22 | Number changed |
| 26 | Non-selected user clearing |
| 27 | Destination out of order |
| 28 | Invalid number format |
| 29 | Facility rejected |
| 30 | Response to STATUS REQUIRY |
| 31 | Normal, unspecified |
| 34 | No circuit/channel available |
| 38 | Network out of order |
| 41 | Temporary failure |
| 42 | Switching equipment congestion |
| 43 | Access information discarded |
| 44 | Requested circuit/channel not available |
| 47 | Resources unavailable, unspecified |
| 49 | Quality of service unavailable |
| 50 | Requested facility not subscribed |
| 57 | Bearer capability not authorized |
| 58 | Bearer capability not presently available |
| 63 | Service or option not available, unspecified |
| 65 | Bearer capability not implemented |
| 66 | Channel type 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 |
| 88 | Incompatible destination |
| 91 | Invalid transit network selection |
| 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 |
| 99 | Information element non-existent or not implemented |
| 100 | Invalid information element contents |
| 101 | Message not compatible with call state |
| 102 | Recovery on timer expiry |
| 111 | Protocol error, unspecified |
| 127 | Interworking, unspecified |
Online-Handbücher
wird das Modem gesprächig und gibt den vom ISDN-Netz übermittelten Grund nach dem