Telecom ISDN Release Cause Codes

Owned by Ujwal Makhija
Sept 01, 2021
2 min read

Whenever a call is made from one telecom system to another, the status’ such as Busy, No Reply etc. are all returned through ISDN Cause Codes. These ISDN cause codes are from 0-127. These are specified by ETSI as a part of ETS 300 102-1.

A summary of this list is as under:

  • 1 - Unallocated (unassigned) 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 enquiry.

  • 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 nonexistent or not implemented.

  • 98 - Message not compatible with call state or message type nonexistent 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.

  • 111 - Protocol error, unspecified.

  • 127 - Interworking, unspecified.

 

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