How to Install DAHDI in CentOS 5
Due to trademark issue with the name Zaptel, Digium changed the name Zaptel to DHADI (Digium Asterisk Hardware Device Interface). Asterisk 1.6.0 and later version will use DAHDI, while Asterisk 1.4 will support both Zaptel and DAHDI. Asterisk 1.2 will be unaffected by these changes.
Download dahdi-linux and dahdi-tools from Digium's website
tar -zxvf dahdi-tools-2.0.0.tar.gz
Install dahdi linux first
and install dahdi tools.
DAHDI is now installed in your system, you can now install Libpri and Asterisk.