The Cisco MC3810 series multiservice access concentrator integrates data, voice/fax, and video signals and connects them to Asynchronous Transfer Mode (ATM), Frame Relay, or leased-line networks. Through its various ports, the Cisco MC3810 series concentrator can support a variety of network and user interfaces, including T1/E1 trunks, serial data ports, an Ethernet LAN connection, private branch exchanges (PBXs), telephone key systems, analog telephones, and Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) services.Voice compression modules (VCMs) and high-performance voice compression modules (HCMs) provide voice compression according to the voice compression-coding algorithm (codec) specified when the Cisco MC3810 is configured. Cisco MC3810 series concentrators have internal mounting spaces for one or two compression modules, depending on the hardware configuration of the chassis. If two mounting spaces are available, any combination of one or two VCM3 and/or VCM6 modules can be installed.