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 Cisco 2800, 2900, 3800 and 3900 Series Unified Communications 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.