The Cisco IP Communications 4-Port FXS/DID Voice/Fax Interface Card 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 Cisco IP Communications voice/fax network module delivers the most versatile combination of analog and digital voice and data capabilities in a single network module.