dialing plan

A dial plan establishes the expected sequence of digits dialed on subscriber premises equipment, such as telephones, in private branch exchange (PBX) systems, or in other telephone switches to effect access to specific telephone networks for telephone calls, and to effect or activate specific telephone system features.

A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reachable by a system of destination code routing. Telephone numbering plans are defined in each of administrative regions of the public switched telephone network (PSTN) and they are also present in private telephone networks.