The Cisco 2600XM/2691/3700 2-Port T1/E1 IP Communications High-Density Digital Voice/Fax Network Module is part of the Cisco Systems® IP Communications suite of solutions. One of three options for high-density digital voice, WAN, and analog voice connectivity and conferencing and transcoding capabilities in a single network module, the NM-HDV2-2T1/E1 version includes two built-in T1/E1 ports and a VIC/VWIC slot that can be fitted with either digital or analog/BRI voice/WAN interface cards. It supports up to 120 channels of digital voice or 60 channels of digital voice and four channels of analog voice in a medium complexity codec. . For flexibility, the IP Communications High-Density Digital Voice/Fax Network Module operates with the Cisco CallManager system with Survivable Remote Site Telephony (SRST) and Cisco CallManager Express.