About Directory Number Routing

A directory number is a 10 digit telephone number which is divided into three parts:

NPA: The first three digits of a telephone number known as Numbering Plan Area (NPA) code.
NXX: The second three digits of a telephone number known as Central Office code is also known as prefix.
Line: The last four digits of a telephone number.

See ASAP System Administrator's Guide for more information about using Design Studio to configure directory numbers on atomic actions in a cartridge project.