I have an asterisk server all setup and running already, what I'm looking to do is call a bunch of numbers and record which calls were to disconnected lines. I've got ${HANGUPCAUSE} writing into the CDR, but it is recording as 0/'NO ANSWER'. Obviously, I need to be able to tell the difference between an unanswered call and a disconnected line.
At the moment, my very simple callplan is ::

exten => _0N.,1,Dial(DAHDI/g0/${EXTEN},20,Tr)
exten => _0N.,n,Set(CDR(userfield)=${HANGUPCAUSE}.${DIALSTATUS})

The plan is to extend this later on to record the disconnects against a customer database using an AGI script.

Have I missed some configuration option? Any suggestions/alternatives would be much appreciated.

I'm using a TDM410P with 4 FXO modules to bridge the SIP phones we have with analog lines provided by Telstraclear.

Cheers.