The Cisco IP Communications voice/fax network modules provide enterprises, managed service providers, and service providers the ability to directly connect the public switched telephone network (PSTN) and traditional telephony equipment to existing Cisco 2600XM Series, Cisco 2691, 3640, and 3660, and Cisco 3700 Series voice gateway routers. This set of Cisco IP Communications voice/fax network modules delivers the most versatile combination of analog and digital voice and data capabilities in a single network module.