363-206-305
Transmission and Synchronization
5-4
Issue 3 June 2000
Wideband Shelf Protection Architectures
5
The eight low-speed interface slots of the DDM-2000 FiberReach wideband shelf
can be configured in two protection architectures: 1x1 protected or 1x7 protected.
(See Note.) In a 1x1 protection configuration, the eight slots are divided into four
low-speed groups — A, B, C, and D. The bottom four slots are the service A, B, C,
and D slots and the top four slots are the associated protection A, B, C, and D
slots. This configuration is most appropriate for applications with a mixture of low-
speed service needs (for example, DS1 and T1 carrier extensions).
NOTE:
A wideband shelf comes with a 1x1 and a 1x7 protection bus module that
goes on the backplane. However to change the protection scheme, it must
be done out of service.
In a 1x7 protection configuration, the eight slots are provisioned as a single low-
speed group with seven service slots and one protection slot. This arrangement is
intended for applications where only one type of low-speed service is needed.
Multiple types of low-speed services (T1 or DS1 only) can be supported at one
time; however only one type will be protected, determined by the type of circuit
pack in the protection slot. In both 1x1 and 1x7 protection architectures, the
protection slot(s) can be left unequipped, leaving the low-speed service
unprotected. The protection architecture can be changed between 1x1 and 1x7
but must be done out of service by installing the appropriate protection module
bus on the rear of the shelf as shown in Figure 3-8 (DDM-2000 FiberReach
Multiplexer Wideband Shelf — Rear View).
Narrowband Shelf Interfaces and Multiplexing
5
The DDM-2000 FiberReach narrowband shelf shares the same channel units as
the
SLC
-2000 MSDT. However, the narrowband shelf can offer up to 12 slots with
a two-DS1 capacity for DS0 services and twice the ISDN services, versus only 6
slots and single DS1 capacity in the MSDT. This provides more flexibility for
special services, such as integrated services digital network (ISDN).
The main controller and interface for the narrowband shelf is the digital signal
cross-connect backplane interface unit (DSXBIU), which interfaces to the 12
channel units via TCPM and RCPM lines for pulse code modulation and the bank
control link (BCL) for provisioning and inventory. See Figure 5-2. Clock generation
and synchronization are controlled by the DSXBIU. A ringing generator unit (RGU)
sends the ringing signal to all of the channel unit slots. A channel and drop test
unit (CDTU) provides the channel and drop testing capability for the narrowband
shelf. The power converter unit (PCU) delivers power to the narrowband shelf. The
DSXBIU communicates with the common units via a serial protocol link called the
microwire link. This link is a serial three-wire clock, transmit, and receive protocol.
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