Messaging supports both 911 and E911 requirements. For traditional telephones calling the 911 emergency number, Messaging uses its automatic routing table to send the emergency call over an ISDN trunk and include the Calling Party Number for automatic identification by the PSAP. In this way, the PSAP, using its Automatic Location Information (ALI) database, can immediately identify the location of the emergency. Alternatively, Messaging can send the call to the Public Safety Answering Point (PSAP) through a Centralized Automatic Message Accounting (CAMA) trunk, which sends Caller Emergency Service Identification (CESID) to the PSAP.
For communications systems supporting geographically dispersed locations for which there are different PSAPs, Messaging supports a separate CAMA, ISDN, or central office trunk for each location so that the 911 call and location identification is sent to the correct PSAP.