Ralph
a good starting point could be:
http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3600/voice/4936vqsg.htm
please note that this is for a 3600 series router, but information is valid for 2600. Also
I am not clear about your router ports, but 2600 comes with 2 WIC slots and 1 network module slot. as fas as I know, VIC ( voice card) should use the network module so you will need a network module.