Page 222 of 254 Emergency Services configurationNN43001-308 Standard 01.02 May 2007For SRG applications, Nortel recommends two alternative general methodsto specify which digit string results in a call to emergency services:• Use the Emergency Services Access (ESA) feature. This is the preferredmethod in North America, the Caribbean and Latin America (CALA),and in those countries that are members of the European Union (EU).ESA provides specific features and capabilities required by legislation inthese jurisdictions.• Use of a special dialing sequence, such as a Special Number (SPN) in theNetwork Alternate Route Selection (NARS) data block. This does notresult in ESA features or capabilities.The main office Call Server forwards emergency services calls to the SRGPSTN. Calls are redirected over a Virtual Trunk using the services of theNRS.Emergency Services Access (ESA)The ESA configuration specifies the digit sequence (a DN) that the user dialsto start an emergency call, known as the Emergency Services DirectoryNumber (ESDN). There can only be one ESA configuration per customer andthus only one ESDN per customer, which means that all telephones on thesame network must be in the same numbering plan.If the SRG and the main office do not use the same ESDN, the SRG mustreplace the incoming digits for the tandem ESA call from the main office withits own ESDN. For more information, see Emergency Services AccessFundamentals (NN43001-613).IMPORTANT!In Normal Mode, an IP Phone must have a Virtual Trunk available andconfigured between the main office and branch office in order tocomplete an emergency services call.IMPORTANT!Do not route ESA calls to a node that has no direct ESA trunks.
