[asterisk-dev] Queue and analog PBX

[Faruk Kasumovic]

I'm trying to do following:

I want to link asterisk queue with analog PBX in fashion that all 
incoming calls will be transfered from queue using flash/recall so 
zaptel channel is free after that.
And I made it, but what if number I flush to is busy, how can I detect 
it before confirming transfer.
I can read from channel but can't see if it is busy signal. If I could 
detect busy tone then I can recall it to queue and wait, then try again.
I try to read frames and check progress state frm->subclass it in first 
frame read 4 as answered, then 0, whats probably wrong way.
Any ideas ? Thanks.