The Cisco VIC-4FXS/DID Analog Voice Interface Card (VIC-4FXS/DID) can operate in both foreign exchange station (FXS) (default setting) and direct-inward-dial (DID) modes on the Cisco 1751 and 1760. On other voice platforms the VIC-4FXS/DID card currently only operates in FXS mode when the card is installed in one of these network modules:
1-slot IP communications voice/fax network module (NM-HD-1V)
2-slot IP communications voice/fax network module (NM-HD-2V)
2-slot IP communications enhanced voice/fax network module (NM-HD-2VE)
IP communications high-density digital voice/fax network module (NM-HDV2)
Upgrade to Cisco IOS Software Release 12.3.(14)T or later in order to use the card in DID mode. In Cisco IOS Software Release 12.3(14)T and later, both modes of operation are available for the VIC-4FXS/DID card when installed on these voice network modules.