4f55f5cb_ISDN_Cause_Codes__Cause_Usage
[Cause#] 97 [Fixit!] N/A [Cause Summary] Message type non-existent or not implemented. [Cause Usage] 
Indicates that the equipment sending this cause has received a message with a message type it does not recognize either because this is a message not defined or defined but not implemented by the equipment sending this cause.
ISDN Cause Codes
Cause Usage