The Cisco IP Communications voice/fax network modules support either one or two Cisco voice interface cards (VICs) or Cisco voice/WAN interface cards (VWICs) and install into network module slots for the Cisco 2800, 2900, 3800, and 3900 series unified communications routers. The Cisco VICs are daughter cards that install into the network modules and provide the interface to the PSTN and to telephony equipment (PBX, key systems, fax machines, phones). The Cisco VWICs are daughter cards that provide the interface to the PBX, PSTN, and/or WAN.