4f55f5cb_ISDN_Cause_Codes__Cause_Usage
[Cause#] 19 [Fixit!] N/A [Cause Summary] No answer from user (user alerted). [Cause Usage] 
Used when a user has provided an alerting indication but has not provided a connect indication within a prescribed period of time. This cause is not necessarily generated by Q.931 procedures but may be generated by internal network timers.
ISDN Cause Codes
Cause Usage