62 / Welcome to ISDNModular ICS 7.1 Installer Guide N0130943 02For information about system programming of this feature, seeProgramming Call by Call service selection on page 475.For services information about dialing plans and PRI, seeNetworking with Norstar on page 109 and Dialing Plan onpage 451.Refer to the hardware section for Call-by-call routing on page499.Emergency 911 dialingModular ICS 7.1 with the ISDN PRI feature is capable oftransmitting the telephone number and internal extensionnumber of a calling station dialing 911 to the Public SwitchedTelephone Network.State and local requirements for support of Emergency 911dialing service by Customer Premises Equipment vary.Consult your local telecommunications service providerregarding compliance with applicable laws and regulations.For most installations, the following configuration rulesshould be followed, unless local regulations require othersettings.• All PSTN connections must be over PRI.• In order for all sets to be reachable from the Public SafetyAnswering Point (PSAP), the system must be configuredfor DID access to all sets. In order to reduce confusion, thedial digits for each telephone should be configured tocorrespond to the extension number (DN).• The OLI digits for each telephone should be identical tothe DID dialed digits for the telephone.• The System Coordinator is responsible for maintaining asite map or location directory that allows emergency
