AT&T DS1/DMi/ISDN-PRI manual Line+Trunk Mode, 6PORT TYPES/INSTALLATION Compatibilities

6-6PORT TYPES/INSTALLATION COMPATIBILITIES

backplane pins 208 and 224. For J58888N1 List 2 Modification C or later, the carrier is manufactured with the strap always installed on slots 0 and 13. The strap may be field installed on slots 5 and 18, as required.

In line-only mode, a DS1 provides the functional equivalent of three analog OPS circuit packs, each containing eight ports. The line-only DS1 thus requires three carrier slots: one for the actual circuit pack and two more as virtual slots. The term virtual is used to represent slots whose backplane signals are used by the line-only mode DS1, but not physically occupied by the interface. Virtual slots result from a physical limitation in the number of time slots that are available in each carrier slot .

Only 8 time slots per carrier slot are available to OPS circuit packs. Since a DS1 uses 24 time slots, it must use the time slots associated with the occupied carrier slot, plus those from 2 additional slots. The two virtual slots associated with the real line-only mode DS1 always occupy the two earner slots immediately to the right of the real DS1.

WARNING: These two virtual slots must be left vacant. Otherwise, circuit packs inserted in these slots may be damaged along with the DS1.

A fully equipped carrier contains four line-only DS1s and has four other slots available for analog- type circuit packs. These other slots are physical slot numbers 3, 8, 16, and 21. Therefore, a single carrier can provide up to 96 digital OPS ports. Figure 6-1,Physical and Virtual Carrier Slot Relationships, Line-Only Mode, shows the carrier slots, physical versus virtual slot locations, and their relationship to OPS port numbers.

Line+Trunk Mode

The line+trunk mode of a DS1 provides the capability of mixing both lines and trunks on the same DS1 facility.

The DS1 works (by default) in line+trunk mode, unless the backplane strap is configured. Here, a DS1 provides the functional equivalent of six analog circuit packs, each providing four ports. The line+trunk DS1 thus requires six slots: one for the actual circuit pack and five as virtual slots. Virtual slots mean the same thing for line+trunk mode as they do for the line-only interface with one variation: virtual slots provide four ports for the line+trunk mode versus eight ports for the line-only mode.

System 85 hardware allows a maximum of four trunk circuits per slot. Therefore, line+trunk mode only uses four backplane time slots from each of the six carrier slots. Thus, a maximum of four OPS ports may be administered for any one of the virtual (or actual) slots.

A maximum of two line+trunk circuit packs may be configured in each carrier. They may only be placed in slots 5 and 18. Therefore, with line+trunk mode, the carrier will support a maximum of 48 digital trunks or 48 OPS ports. Virtual slots are the leftmost three slots of the left quarter and the two slots immediately to the right of the real DS1 in the right quarter of the half carrier in which the DS1 is contained. These virtual board locations must be left vacant or damage to a port board and the DS1 could result.