Network Trunk Module
Subrate Interface Card (BC-SR)
The back card/subrate (BC-SR) terminates subrate trunks on the NTM. A subrate trunk uses part of the E1 or T1 bandwidth. The BC-SR typically functions in tail circuits or where little traffic exists.
A subrate trunk facility interface operates in DCE mode, and the subrate channel functions like a synchronous data channel. Therefore, the IGX BC-SR always operates in DTE mode. Only leased lines are supported (no dial-up lines). Subrate trunks cannot pass clock signals between nodes.The BC-SR provides the following:
Trunk line interfaces to subrate trunks
Trunk rates of: 256 Kbps, 384 Kbps, 512 Kbps, 768 Kbps, 1.024 Mbps, 1.536 Mbps, 1.920 Mbps
V.11/X.21, V.35, and EIA/TIA-449 interfaces
Synchronization of the trunk clocking with looped clock option (not applicable to X.21)
A limited set of EIA control leads monitored by the system
Figure 4-25and Table 4-19describe the BC-SR faceplate. When you correlate the figure and table, read from the top down.
Table 4-20lists the data signals and EIA leads supported by the subrate interface.
4-42Cisco IGX 8400 Series Reference
