NM-HDV card is a network module that can support up to 60 VOIP ports. It also has a slot in it for installation of a 1 or 2 E1 or T1 PRI VWIC card. Installation of the complete assembly (for example an NM-HDV-2E1-60) in a router would provide a full voice gateway. More recent routers may also have internal advanced integration modules (AIM) slots - basically attaches to the mainboard inside the router to either add features such as voice, voicemail, VPN, security, and compression. Finally, some of these routers have removable PCMCIA or compact flash storage modules.
VOIP Configurations: Cisco modular routers can be configured for VOIP several way. First, an NM-HDV (voice NM card) can beClick for full size image. Cisco 2651XM with NM-HDV-2E1-60 or 2T1-48. 2600/2600XM series. installed with 12 port voice DSPs (PVDM-12) and either a T1 or E1 VWIC card. This makes the router into the equivalent of a VOIP gateway - and each NM-HDV card combination set will provide up to 2 PRIs of voice capabilities. So a 2600XM series router can provide 2 PRIs or voice, a 3640 can provide 4, and the 3662 can provide 8. Second, some routers have internal AIM card slots. If a T1/E1 VWIC card is installed in a WIC slot and an AIM voice module is installed in the AIM slot, the router can support 1 E1/T1 of voice traffic. In this way, even the 1751-V (a small office/home office router) can support VOIP traffic. Third, some routers have built-in PVDM (voice chip) sockets, and PVDM FXS/FXO cards can be installed.