FAX through DAHDI


I have a setup as follows


Asterisk is running version and DAHDI. I can make and receive voice calls to and from PSTN.

But I am having no success with sending and receiving fax to and from PSTN.

The ATA support T.38. I am thinking of using app_fax so that Asterisk can receive fax and send fax through DAHDI.

Can anyone send me a sample example as to how to do this in the dial plan ?