Dial plan

A dialing plan establishes the permitted sequences of digits dialed on subscriber or station lines with subscriber premises equipment, such as telephones and private branch exchange (PBX) systems. Dialing plans in the public switch telephone network (PSTN) have traditionally been more commonly referred to as dialing procedures. The dialing plan of a private telephone system or a customer premise equipment, such as an analog telephone adapter (ATA) or an IP phone, is sometimes also called dial plan. The digit sequences (numbers) permissible in a dialing plan may be as short as a single digit, e.g. for reaching an operator, or as long as a complete international telephone number, including trunk prefixes and international prefixes.

Similarly, telephony service operators may provide dialing sequences for special services, such as directory assistance and emergency services.

PBX equipment, carrier switching systems, or end-user telephones may specify a variable-length dial plan or a fixed-length dial plan. In private branch exchanges in the U.S. a dialing plan may specify the addresses for the following destinations:

Analog telephone adapters, IP phones, and many other VoIP media gateways have configuration options that establish the digit sequences that can be dialed with the equipment. The dial plan of these devices is established by a digit map. The following syntax may be used for such dial plan, as adapted from RFC 2705, the specification for the Media Gateway Control Protocol.

Some dial plan examples using the above syntax look as follows:

This page was last edited on 22 December 2017, at 09:01.
Reference: https://en.wikipedia.org/wiki/Dialing_plan under CC BY-SA license.

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