Nortel Networks BCM1000 manual Setting Offsets

Chapter 4 Selecting the media bay modules for your system 63

Setting Offsets

Each offset is one-quarter of a DS30 bus. Each DS30 bus, supports 16 lines (32 time slots) for most trunk modules.

Exceptions:

•DTM modules support 23 to 30 lines per bus

•FEM modules, where each DS30 bus supports one Norstar fiber module connection.

For station modules, each bus supports 16 telephones or telephony devices for station modules that support single density, or which are set to single density, in the case of the DSM16+ and DSM32+, or on DS30 06 and 07 if the system remains set to Partial Double Density (PDD). On each bus that supports double density, DSM16+ and DSM32+ modules set to double density have access to eight telephones per offset, for a total of 32 telephones per DS30 bus if the offsets are fully loaded.

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

Modules that can have offsets assigned include CTM, CTM8, GATM4, GATM8, BRI, and ASM 8/ ASM8+. For example, two CTM 8s can be assigned to the same DS30 bus number, with different offset numbers. However, you cannot assign a CTM8 and an BRI module to the same DS30 bus.

ASM8/ASM8+ modules can only be installed on two offsets on a DS30 set to PPD. However, on a DS30 in FDD, ASM8/ASM8+ modules can be supported on all four offsets. Note that there is no double-density dip switch setting for these modules.

Offsets are assigned using DIP switches 1, 2, and 3 on the media bay module.

Note: Media bay modules that do not or cannot share DS30 bus blocks always assign the offset as 0 (zero). As well, if the module requires more than one DS30 bus, such as the 4x16 module, only the first DS30 bus is set on the DIP switches. The next consecutive DS30 bus number is automatically assigned by the module.

Figure 26 shows how a DS30 bus containing 16 line connections is broken down into four offset groups of four lines each.

Figure 26 Offsets are part of DS30 line/DN groups

Each offset supports:	Offset 0	1 DS30 bus supports:
four lines (trunks)*	Offset 1
four DNs (single density)	Offset 2	16 lines (trunks)*
eight DNs (double density)		16	DNs/32 time slots (Partial Double Density)
	Offset 3	32	DNs/32 time slots (Full Double Density)

*DTM: 6 to 8 lines per offset (24 to 30 lines per DS30)

*FEM: DS30 = 1 port

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