Nortel Networks 400 4.0 用户手册

Chapter 8 Installing a media bay module (MBM)

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Figure 64   DS30 model

DS30 numbers are set using the number 4, 5, and 6 DIP switches on the back or underside of the 
MBMs. The exception is the FEM MBM. The FEM DIP switches turn on ports, each of which 
consumes one bus.

Each offset represents one-quarter of a DS30 bus. Each bus supports 16 lines (32 time slots) for 
most MBMs. 

Exceptions: 

•

DTM MBMs, which support 23 to 30 lines per bus

•

FEM MBMs, where each bus supports one Norstar fiber module connection.

Offsets are numbered 0, 1, 2, and 3. MBMs that require less than a full bus can be assigned a DS30 
number and an offset number. This allows more than one MBM to be assigned the same DS30 
number, but with a different offset number.

MBMs that can have offsets assigned include CTM4, CTM8, BRIM S/T, ASM8+, and GASM8. 
For example, two CTM8s can be assigned to the same DS30 number, with different offset 
numbers. However, you cannot assign a CTM8 and a BRIM to the same DS30.

The 32 time slots are important when you are working with station MBMs. The DSM16+, 
DSM32+, ASM8+, and GASM8 can be configured, using the offset DIP switches, to use 
each of these time slots as separate telephone lines. This, essentially, doubles your system 
telephone capacity.

DS256
on MSC

DS30 bus #2

DS30 bus #3

DS30 bus #4

DS30 bus #5

DS30 bus #6

DS30 bus #7

DS30 buses 
available to modules 
in a 2/6 split

Four offsets per bus

DS30 buses 
available to modules 
in a 3/5 split