The Cisco High-Density Analog & Digital Extension Module for Voice & Fax (EVM-HD) provides enterprises, managed service providers & service providers the ability to directly connect public-switched telephone networks (PSTNs) & existing telephony equipment to Cisco 2821, Cisco 2851, Cisco 3825, & Cisco 3845 integrated services routers. With support for up to 24 total voice & fax sessions, the Cisco High-Density Extension Module is ideal for networks with high analog (foreign exchange station [FXS], direct inward dialing [DID], & foreign exchange office [FXO]) & digital (Basic Rate Interface [BRI]) call-capacity requirements. The Cisco High-Density Analog & Digital Extension Module for Voice & Fax (EVM-HD) is an industry-leading voice & fax interface module for Cisco 2821, Cisco 2851, Cisco 3825, & Cisco 3845 integrated services routers. It helps enable packet voice technologies with support for voice over IP (Vo IP), including H.323, Media Gateway Control Protocol (MGCP) & Session Initiation Protocol (SIP); voice over Frame Relay (Vo FR), & voice over ATM (Vo ATM), including ATM Adaptation Layer 2 (AAL2) & AAL5. The Cisco High-Density Extension Module allows Cisco 2821, Cisco 2851, Cisco 3825, & Cisco 3845 routers to connect directly to the PSTN & existing telephony equipment (for example, private branch exchange (PBX), Key system, analog telephones, & analog fax machines) through standard analog (FXS, DID, & FXO) & digital (BRI) interfaces. The High-Density Extension Module supports telephony toll bypass, new packet telephony applications, & full gateway integration within the Cisco AVVID (Architecture for Voice, Video & Integrated Data) IP telephony design. With support for up to 24 total voice & fax sessions, the Cisco High-Density Extension Module is ideal for networks with high analog & BRI call-capacity requirements.