The Cisco 12000 Series Two-Port Channelized OC-3c/STM-1c (DS1/E1) Line Card (2-Port CHOC-3) provides advanced DS-1/E-1 aggregation, with two optical connections. Each interface, when configured in SDH framing mode, is capable of supporting channelization into 63 independent E-1 (VC-12 mapping) channels in an SDH configuration. When configured for SONET framing mode, each interface is capable of supporting channelization into 84 independent DS-1 (VT1.5 mapping or CT-3 mapping into STS-1) channels in a SONET configuration. Fractional E-1 and individual 64 kbps channels can also be configured, up to the limit of 105 channel-group definitions per STM-1 (35 per TUG-3). Fractional T-1 and individual DS-0 channels can also be configured, up to the limit of 35 channel-group definitions per STS-1 (210 per line card). Each Cisco 2-Port CHOC-3 Line Card supports up to 126 E-1 connections in an SDH configuration and 168 DS-1 connections in a SONET configuration, or any combination of DS-0/64 kbps, fractional T-1/E-1, and T-1/E-1 interface definitions up to 210 channel groups per line card.