AT&T DS1/DMi/ISDN-PRI manual System 85 DS1 or DMI-MOS, Traditional Modules ANN35, Operating Mode

PORT TYPES/INSTALLATION COMPATIBILITIES 6-13

channel signaling bits must be passed directly between two DS1/DMI ports without any switch processing software interaction. Any DS1/DMI port, regardless of its operating mode, may be switched into its corresponding transparent mode through administration. Additional details about DS1/DMI port types can be found in the DSC feature reference.

SYSTEM 85 DS1 OR DMI-MOS, TRADITIONAL MODULES (ANN35)

The operating mode and supported port types for System 85 DS1 of DMI-MOS (ANN35) in traditional modules are described next.

Operating Mode

DMI-MOS only works in trunk mode and it does not support line mode capabilities. The backplane strap, which may optionally be used for DMI-BOS, must not be configured. Here, DMI-MOS provides the functional equivalent of six analog circuit packs, each providing four ports, but using message-oriented-signaling. Therefore, the DMI-MOS requires six slots: one for the actual circuit pack and five as virtual slots. Each virtual slot provides four ports.

System 85 hardware allows a maximum of four trunk circuits per slot. Therefore, this mode only uses four backplane time-slots from each of six carrier slots (24 time-slots producing 24 DMI-MOS channels).

Amaximum of two DMI-MOS trunk-mode circuit packs may be configured in each DS1 or MFAT carrier. They may only be placed in slots 5 and 18. Virtual slots are the leftmost three slots of the left quarter and the two slots immediately to the right of the real DMI-MOS in the right quarter of the half carrier in which the interface is contained.

CAUTION: These virtual slots must be left vacant or damage to a port board and the DMI could result.

With R2V4 and later versions, a DS1 or MFAT carrier may be configured with both DMI-MOS and DMI-BOS circuit packs. Recall that the DMI-BOS circuit pack may be used to provide either line+trunk mode or line-only mode. When the two are mixed within the same carrier, the appropriate restrictions apply to each; refer to Operating Modes under the heading Generic 2 DS1/DMI-BOS.

A carrier equipped with two trunk mode DMI-MOSs will have four slots available for other port boards in physical slots 3, 8, 16, and 21. Figure 6-2,Physical and Virtual Carrier Slot Relationships, Line+Trunk Mode, shows the carrier slots, physical versus virtual slot locations, and their relationship to trunk mode and/or line+trunk Mode use.