Lucent Technologies SLC-2000 User & Service Manual page 70

363-208-001
Product Description
A received OC-1 signal is converted back to an electrical STS-1. This STS-1 is
descrambled and demultiplexed and transport/path overhead is accessed. Some
of the overhead (for example, section data communications channel) is passed by
means of serial data links to the control packs, while other bytes (for example,
framing, parity check) are processed on-board. The STS-1 signals go through a
pointer processor to guarantee STS-1 frame alignment to the local system clock
before being routed to the other Main and Function Unit slots.
If an incoming STS-1 signal from the fiber is to be VT1.5 cross-connected, VT1.5
pointer-processing is performed on this pack and STS-1 path overhead
termination is performed on these signals. All signals entering this pack from
either the backplane or from the optical interface may be routed as STS-1s. If
appropriate, VT1.5 routings may be established between STS-1s using a limited
VT1.5 cross-connection.
Each 27G-U OLIU circuit pack provides timing signals to and receives timing
signals from the TGS circuit packs.
Multiplexer Applications
The FUNCTION A slots are equipped with multiplexer units that convert the virtual
tributary groups (VT-Gs) (containing the DS1s) into an STS-1 signal.
VT to STS-1 Multiplexer (MXRVO)
The VT to STS-1 BBG2 multiplexer circuit pack (MXRVO) multiplexes seven VT-G
signals from the VTU packs (in the DS1/VT feeder interface) or from the DS1
packs (in the DS1 distribution section) into an STS-1 signal.
DS1 Low-Speed Interface Section (Eight Slots)
The DS1 low-speed interface section (Figure 2-4) provides DS1 distribution from
the "C" SONET multiplexer group (FUNCTION C) for up to 28 DS1 pipes
(customer DS1 inputs). Each slot in this section accepts up to four DS1 signals (at
standard DSX-1 levels) for clear channel transport.
The slots are protected using a 1x N configuration, where N = 1 to 7 depending on
the number of equipped slots. The 177A retainer card is used in the empty slots in
this section so that protection switching will operate properly. If the retainer card is
not used, transmission may be corrupted. The maximum number of circuit packs
in this section is eight (1 through 7 service plus P for protection).
The DS1 circuit pack (BBF1B or BBF3) interfaces the DSX-1 on the low-speed
side and the "C" SONET multiplexer group on the high-speed side. The DS1
circuit pack multiplexes four external DS1 interfaces into a SONET virtual tributary
(VT) group (VT-G) signal. The VT-G is an intermediate step in multiplexing
between DS1 and STS-1 signals and contains four DS1 signals.
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Issue 9 April 1998
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