That depends upon the customer requirement. If he needs connectivity to PSTN through PRI, you need to choose VWIC-1MFT-T1/E1 card or VIC2-4FXO card. If the site would like to use local DSP resources for conferencing or transcoding for local calls at that site, then you may need to provision additional PVDM resources like PVDM2-32 or PVDM2-64.
Regards...
-Ashok.
With best regards...
Ashok