NA-ESRK
North American Emergency Services Routing Key
A telephone number in the North American Numbering Plan assigned to an emergency services call by a North American Visited PLMN (Public Land Mobile Network) for the duration of the call. The NA-ESRK is used to identify both the emergency services provider and the switch in the Visited PLMN currently serving the emergency caller. During the lifetime of an emergency services call, the NA-ESRK also identifies the calling mobile subscriber.