ESRD (Emergency Services Routing Digit)

Either a 10-digit North American Numbering plan or non-NANPA number that uniquely identifies a base station, cell site, or sector that is used to route wireless emergency calls through the network. The ESRD may also be used by the PSAP to retrieve the associated ALI data. In the past, these numbers may have been dialable or non-dialable. As of second 2012 these numbers should be non-dialable, and all new ESRDs will be non-NANPA, non-dialable ten-digit numbers.