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 (private branch exchange [PBX], key system, analog telephones, fax machines, etc.) 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. As a completely integrated component of the Cisco IP Communications solution including Cisco CallManager, Cisco IP phones, Cisco Unity™ unified messaging software, Cisco IP Contact Center (IPCC), and the entire line of Cisco IP Communications products, the Cisco IP Communications voice/fax network modules are a cornerstone of Cisco AVVID (Architecture for Voice, Video, and Integrated Data). When used in a Cisco voice gateway router with Cisco CallManager, Survivable Remote Site Telephony (SRST), or Cisco IOS® Telephony Service, the Cisco IP Communications voice/fax network module is a complete IP Communications solution for the business branch.