ESRK (Emergency Services Routing Key)

Either a 10-digit North American Numbering plan or non-NANPA number that uniquely identifies a wireless emergency call, is used to route the call through the network, and used to retrieve the associated ALI data. In the past, these numbers may have been dialable or non-dialable. As of 2012 these numbers should be non-dialable, and all new ESRKs will be non-NANPA, non-dialable ten-digit numbers.