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318 Telephony Hardware Selection and Settings
P0993133 03
Setting offsets
Each offset is one-quarter of a DS30 bus. Each bus, supports 16 lines (32 time slots) for most
modules.
Exceptions:
• DTM modules support 23 to 30 lines per channel
• FEM modules, where each bus supports one Norstar fiber module connection.
Offsets are numbered 0, 1, 2, and 3. Modules that require less than a full bus can be assigned a
DS30 number and an offset number. This allows more than one module to be assigned the same
DS30 number, but with a different offset number.
Modules that can have offsets assigned include CTM, CTM8, BRIM S/T, and ASM 8. For
example, two CTM 8s can be assigned to the same DS30 number, with different offset numbers.
However, you cannot assign a CTM8 and an BRI module to the same DS30.
Offsets are assigned using DIP switches 1, 2, and 3 on the media bay module.
Figure 194 shows a DS30 broken down into four offset groups of four (single density) or eight
(double density) lines each. Once again, note that when you enable a station module for double
density, the line numbers double.
Note: Double Density
The 32 time slots are important when you are working with station media bay modules.
The DSM 16+, DSM 32+, and ASM 8 modules 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. On a default 3.0 system, this feature, called
Partial Double Density (PDD), is available on DS30 2, 3, 4, and 5. DS30 6 and 7 maintain
the current two time slots per line configuration, which supports the Companion
application. For systems where Companion is not required, you can use the Unified
Manager to change all six DS30 buses to FDD.
Exception: If your system has a 3/5 channel split, only DS30 6 becomes double density
and is available to media bay modules when the system is changed to FDD. However, 16
more channels on DS30 7 are also made available for IP telephones.
Note: Media bay modules that do not or cannot share DS30 buses always assign the offset
as 0 (zero). As well, if the module requires more than one bus, such as the 4x16 module or
the DDIM, only the first DS30 is set on the DIP switches. The next consecutive DS30
channel number is automatically assigned by the module.