Hi
You need to first consider what you need the VICs for - i.e. what type of PSTN circuits are available to you, how many channels you need, etc.
You then need to select an appropriate card that is compatible with your router - for a 28xx this is typically a VIC2-something, but check here : http://www.cisco.com/en/US/partner/products/hw/routers/ps259/products_tech_note09186a00800e73f6.shtml
Finally, depending on the number of channels you need, you then specify PVDM modules : http://www.cisco.com/cgi-bin/Support/DSP/cisco_prodsel.pl
Regards
Aaron
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Aaron
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