AT&T DS1/DMi/ISDN-PRI manual DMI-BOS Trunks, Did Trunk, Ground-Start CO Trunk

PORT TYPES/INSTALLATION COMPATIBILITIES 6-11

interface. They differ in their analog voice interfaces (2- or 4-wire) and in what type of E&M (analog) signaling to which the DS1/DMI signaling states are converted (type-I, II, or III).

ASystem 85 analog tie trunk is a 4-wire type-I E&M trunk. Thus, a DS1/DMI tie-trunk port can be considered to be the same, and a 4-wire type-I channel unit (or its equivalent) could be used to interface to a DS1/DMI tie trunk port at the far end.

It appears that any of the other five types of E&M channel units could be used as well, although this capability has not been tested.

DMI-BOS Trunks

DMI-BOS trunks are used to provide 64K-bps data connectivity to a host computer or to provide both voice and 64K-bps data connectivity to private or public networks that support DMI-BOS signaling. These trunks must be optioned for the 24th-channel signaling format.

DID Trunk

The digital DID trunks appear to switch software the same as an SN232 analog DID trunk. Therefore, things that can be administered for an analog DID trunk can also be administered for a digital DID trunk.

The DID trunks are supported by dial-pulse D4-channel bank channel units. The digital DID trunks function as a dial-pulse terminating (DPT) channel unit. They should terminate on a dial-pulse originating (DPO) channel unit (or its equivalent) at the far end.

Ground-Start CO Trunk

The digital ground-start CO trunks appear to switch software the same as a SN230B analog ground- start CO trunk. Therefore, things that can be administered for an analog Ground-Start trunk can also be administered on its digital counterpart.

Ground-start CO trunks are supported by either FX or special-access D4-channel units. Each of these units provides the same function, but they use different digital signaling bit states to represent CO trunk call states (the special-access units have some bits inverted relative to the FX units). Special-access channel units are used primarily in Canada. This use of special-access channel units should not be confused with the 4ESS special-access connection capability.

For Generic 2, the type of channel units DS1/DMI ground-start ports will work with is controlled by administration, but is now restricted to the FX format. A DS1 ground-start CO trunk port will act as a FX subscriber end (FXS) channel unit operating in the ground-start signaling mode. The trunk port should terminate on a FX office (FXO) end channel unit (or its equivalent), which also operates in the ground-start signaling mode.

When the special-access option is administered, the DS1 ground-start CO trunk port will act as a special-access subscriber (SAS) end channel unit operating in the ground-start signaling mode. The trunk port should terminate on a special-access office (SAO) end channel unit (or its equivalent), which also operates in the Ground-Start signaling mode.