Circuit Pack Descriptions
7-30 Issue 8.0 July 2002
Table 7-3 shows the OC-3/OC-12 section DCC bytes that are provided by the
TOHCTL circuit pack.
Overhead Access Local Area Network Interface. 7The overhead access local area
network (OALAN) interface allows the TOHCTL circuit pack to communicate with
the OHCTL (TERM) and SYSCTL circuit packs. The OHCTL (TERM) circuit pack
performs protocol processing for layers 1 through 3 of the OSI 7-layer stack for
the OC-48 section DCC. The SYSCTL circuit pack allows users to access the
OC-3/OC-12 section DCC using the CIT, serial telemetry, and message-based
operations system (X.25) interfaces for single-ended operations.
Power Circuitry 7
TheTOHCTLcircuitpackreceivestwosourcesof−48 volts that are diode OR'd,
fused, and filtered. A modular DC-to-DC power converter produces +5 volts used
on the circuit pack.
The TOHCTL circuit pack monitors the two −48 volt sources to the circuit pack. If
the TOHCTL circuit pack detects a failure of the onboard fuse or power converter,
the red FAULT LED will light. If the fuse or power converter fails, the SYSCTL
circuit pack provides +5 volts to light the FAULT LED on the TOHCTL circuit pack.
Table 7-3. Overhead Bytes
Name Overhead Byte Data Rate Access
DCC D1-D3 192 kb/s System Controller
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