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Circuit Pack Descriptions
Issue 1 December 1997 7-41
General Description of Operation 7
The BBG12 3STS1E circuit pack provides bidirectional transport of three EC-1
signals through the DDM-2000 OC-12 Multiplexer. The 3STS1E circuit pack
performs maintenance and provisioning functions associated with the STS-1 and
EC-1 signals. The 3STS1E circuit pack interfaces to the TSI circuit pack at the
STS-1 rate, to the STSX-1, and to the SYSCTL, and it receives timing signals
from the TSI circuit pack.
Detailed Description of Operation 7
Transmission Circuitry 7
Transmit Direction. 7Figure 7-17 provides an overall block diagram of the BBG12
3STS1E circuit pack. The transmit direction is the direction towards the fiber and
the receive direction refers to the direction towards the STSX-1. In the transmit
direction, the BBG12 3STS1E receives up to three incoming B3ZS encoded EC-1
signals from the STSX-1 cross-connection panel. A closed protection relay
contact routes each EC-1 signal to a circuit that splits the signal and sends one
output to the companion (standby) circuit pack and the other to its own receiver.
The BBG12 3STS1E receiver performs equalization and clock recovery, B3ZS
decoding, and optional automatic AIS insertion. It performs pointer processing on
the input data stream and outputs three corresponding data streams, time-aligned
with a single frame signal, to the TSI circuit packs.
Receive Direction. 7The BBG12 3STS1E receives two STS-1 data signal inputs
for each of the three EC-1 channels: one from the working TSI circuit pack and
one from the standby TSI circuit pack. A jumper allows the user to insert or
remove a LBO network (225 ft. of 734A-type cable equivalent) to provide the
required signal level and shape at the STSX-1 cross-connection panel.
Control Circuitry 7
The BBG12 3STS1E circuit pack interfaces with the SYSCTL circuit pack via the
intra-shelf control bus. The BBG12 3STS1E circuit pack provides maintenance
elements for reporting the status of the circuit pack, status of the incoming STS-1
and EC-1 signals, as well as the circuit pack inventory information (
CLEI
code,
date of manufacture, etc.). These maintenance elements are used by the
SYSCTL for fault detection and isolation. Conversely, the BBG12 3STS1E
responds to control signals from the SYSCTL (such as active and fault LED
controls).
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