The DS3 NI-2 card connects to the xTU-C line cards through point-to-point serial data buses on the backplane, controls timing and redundancy provides CO facility alarm relay contact interfaces and an alarm cut-off (ACO) button, provides visual and audible operating status alerts, contains the ATM switch fabric. It provides the network DS3 WAN trunk interface through BNC connectors located on the system I/O card, provides two DS3 subtend interfaces through BNC connectors located on the system I/O card. This card also supports the aggregation of up to 12 subtended node chassis that are configured for DS3 operation in a tree topology, supports NI-2 card cold redundancy and provides Cisco IOS-based ATM Quality of Service (QoS).