ETSI PRI 13-7
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
Prefixing to calling party number
With calls originated on ETSI PRI trunks, one of the following occurs:
• Both the OTG and OSLC are prefixed to the calling party number—The
OSID TRKGRP parameter (the logical OSID) must be set to the switch
ID of the adjacent node (Meridian 1). The logical OTG is extracted using
the received OTG, logical OSID, and OSLC digits to construct an index
into the OSLC table.
• Only the OSLC is prefixed to the calling party number—The OSID
TRKGRP parameter must be set to NIL to indicate the user will be
identified using the physical OSID/OTG. The logical OTG is extracted
from the OSLC table using the physical OTG (defined by table
MCLLICDR for the current originating trunk group), physical OSID
(defined by office parameter NCS_SWITCH_ID), and OSLC digits to
construct the index. The OSID TRKGRP parameter is NIL, therefore the
logical OSID is obtained from the NCS_SWITCH_ID office parameter.
• Neither the OTG nor OSLC are prefixed to the calling party
number—The OSID TRKGRP parameter must be set to NIL to indicate
the user will be identified using the physical OSID/OTG. The logical
OSID and logical OTC are NIL and 0. Therefore, routing based on the
logical OSID/OTG does not occur.
The OTG and OSLC digits are removed before translations are attempted.
After the OTG and OSLC digits are removed, if the length of the address
digits is greater than 15, only the first 15 digits are used for translations. The
remaining digits are ignored.
Logical OTG
When the first four digits of the called party number and the OSLC digits are
received, they are removed from the incoming called party number before
pretranslations. The DMS-250 switch does the following with the logical
OTG:
• sends it to the dedicated access point (DAP) as the OTG in a dedicated
access line (DAL) and overflow call procedure requests
• records it in billing as the OTG in the A field
• outpulses it in the Generic Digits parameter of the Initial Address
Message (IAM) as the OTG
The physical OSID/OTG is used (unless the logical OSID/OTG was
received) to optionally retrieve an alternate index into table GPXHEAD
(Global Prefix Head). This table is accessed to optionally override the
existing pretranslator name. The remaining called party number digits are
sent through pretranslations.
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