[Asterisk-Users] IAX busy signalling?

[Roy Sigurd Karlsbakk]

Hi

I have a system with one asterisk box in front and a few PSTN gateways 
in the back. When a call comes from PSTN, it's directly forwarded to 
the edge/user asterisk box.

Now if a number is dialled, and that number is not in use, blocked due 
to lack of paying etc, I want to signal that back to the PSTN gateway, 
making this playback or playtones to avoid picking up the phone.

Can someone tell me how? please?

roy