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PORT 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