Nortel SRG200 Configuration Manual page 223

Emergency Services configuration Page 223 of 254
With all sites using the same ESDN, a conflict occurs in the NRS. The
conflict is resolved by using a unique prefix for each site that the main office
adds as it routes the call. The suggested prefix is the ESN home location code
of the SRG, or alternately, the Numbering Plan Area (NPA) code of the SRG
if there is not more than one Call Server in the NPA. Virtually any unique
string can be used as a prefix, because the call is sent to the NRS as an Special
Number (SPN). In the NRS, SPNs have their own separate numbering plan.
The Automatic Number Identification (ANI) data sent to the Public Safety
Answering Point (PSAP) identifies the location of the caller. In some
constituencies, legislation requires one DID per fixed number of square feet,
so the physical location of the emergency can be approximated based on the
telephone number delivered to the PSAP. The ESA feature has a
comprehensive scheme that can be used to convert an extension into an
appropriate DID.
If the branch office is relatively small, it can be easier to use a single DID
number for the branch office. For more information, see Software
InputOutput Reference—Maintenance (NN43001-711).
Routing Emergency Services Access (ESA) calls
IMPORTANT!
Do not route ESA calls to a node that has no direct ESA trunks.
Ideally, route ESA calls directly over Central Office (CO) trunks to the Public
Safety Answering Point (PSAP). In those cases where this routing is not
possible, do not route ESA calls to nodes that have no direct ESA trunks.
Main Office Configuration for SRG200/400 Release 1.5 Configuration Guide