Call failed Cause Code 18

I am making a call to a specific number. It fails with a cause code 18. What does this mean???

[quote=“http://networking.ringofsaturn.com/Routers/isdncausecodes.php”]Cause No. 18 - no user responding.
This cause is used when a called party does not respond to a call establishment message with either an alerting or connect indication within the prescribed period of time allocated.[/quote]

A far end fault.

If you are not using a pure ISDN system, the code may be a translation from some other code. E.g., if it is SIP, look at the source code of chan_sip.c for the translation. The translation will be the nearest practicable ISDN cause code.