AT&T DS1/DMi/ISDN-PRI manual Loop-Start CO Trunk, Of-Premises Stations, Transparent Ports

6-12PORT TYPES/INSTALLATION COMPATIBILITIES

Loop-Start CO Trunk

Generic 2 does not provide an analog equivalent of a DS1 loop-start CO trunk. It is only available as a digital trunk. Use of the loop-start CO trunk is not recommended because of inherent glare and disconnect supervision problems associated with this trunk type.

The DS1/DMI loop-start CO trunk appears to the switch software the same as a ground-start CO trunk. However, to the far end, a DS1/DMI loop-start CO trunk port appears as a loop-start CO trunk. This trunk is provided with present switch software capabilities and conversions performed by the DS1/DMI microprocessor.

The DS1/DMI supports loop-start CO trunks using either FX or special-access D4-channel bank units. The loop-start CO trunk port will act as a FX station (FXS) end channel unit operating in the loop- start mode. The trunk port should terminate at a FXO end channel unit (or its equivalent) operating in the loop-start mode.

When the special-access option is provided by administration software (Generic 2), then the loop- start CO trunk port acts as a SAS end channel unit operating in the loop-start mode. The trunk port should terminate at a SAS end channel unit (or its equivalent) operating in the loop-start mode. This configuration works fine in private networks. However, avoid this configuration when connecting to the public network.

Of-Premises Stations

Generic 2 administration software allows DS1/DMI channels to be administered as off-premises stations, for both the line-only mode and line+trunk mode. A DS1/DMI OPS port appears to switch software the same as a SN221, SN222, SN228, or SN229 analog port would appear, but with one exception: digital OPS ports do not support the Message Waiting feature. The reason is that no D4- channel bank units provide Message Waiting. Therefore, Message Waiting should be turned off when digital OPS ports are administered. The D4-channel bank may support OPS with either the FX or special-access channel units. However, for this port type the office-end channel unit is considered a Generic 2.

By default, OPS ports function the same as FXO end channel units operating in loop-start mode. The ports should terminate at a FXS end channel unit that is configured to operate in loop-start mode.

When Generic 2 administration software allows the special-access channel unit option, then the OPS port will act as a SAO end channel unit operating in the loop-start mode. The port should terminate at a SAS end channel unit operating in the loop-start mode at the D4-channel bank (far end).

The channel units used to support DS1/DMI OPS ports should be connected to a noninterrupted ringing supply in the D4-channel bank. Ringing for these ports is interrupted by the switch.

Transparent Ports

All System 85 or Generic 2 DS1/DMI ports have a transparent signaling mode. There does not exist an equivalent signaling method for analog ports. The transparent signaling mode permits direct access to a DS1/DMI channel’s signaling bits. This function is necessary for DSCs, where DS1/DMI