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Circuit Pack Descriptions
7-92 Issue 3 June 2001
Figure 7-35. TMUX Circuit Pack
General Description of Operation 7
The BBG20 TMUX circuit pack provides bidirectional transport of one DS3 signal
through the DDM-2000 OC-3 shelf.
In the transmit direction, the BBG20 TMUX circuit pack accepts one 44.736 Mb/s
bipolar 3-zero substitution (B3ZS) coded DS3 signal and demultiplexes it into 28
DS1s. Performance monitoring is performed on the DS1s before they are mapped
into floating VT1.5s. The 28 VT1.5s are then multiplexed into an STS-1 payload
envelope using SONET asynchronous mapping. The STS-1 path overhead and
pointer bytes are added and the resulting signal is sent to the high-speed OLIU
circuit pack.
In the receive direction the reverse process takes place: The STS-1 signal from
the OLIU circuit pack goes through STS-1 pointer interpretation, path overhead is
FAULT
AT & T
x
x
S1:1
x
x
x
ACTIVE
TMUX
BBG20
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