The voice functionality built into Cisco IOS software enables modular access routers to carry voice traffic, such as telephone calls & faxes, as Voice over IP (Vo IP) simultaneously with data traffic over LANs, MANs, & WANs. Voice network modules convert telephone voice signals into a form that can be transmitted over an IP network. Voice network modules convert telephone voice signals into a form that can be transmitted over an IP network. NM-HD-2V= is a 2-slot 8-channel High-Density Network Module.