telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...

, a dial plan (or dialing plan) establishes the permitted sequences of digits dialed by telephone subscriber and the manner in which a telephone switch interprets these digits within the definitions of the prevailing

telephone numbering plan A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone number A telephone number is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or ...

. Dial plans in the

public switched telephone network The public switched telephone network (PSTN) provides Communications infrastructure, infrastructure and services for public Telecommunications, telecommunication. The PSTN is the aggregate of the world's circuit-switched telephone networks that ...

(PSTN) have traditionally been more commonly referred to as ''dialing procedures''. The collection of permissible digit patterns, so called ''digit-maps'', for a private telephone system or for customer premise equipment, such as an

analog telephone adapter An analog telephone adapter (ATA) is a device for connecting traditional analog telephones, fax machines, and similar customer-premises devices to a digital telephone system or a voice over IP telephony network. An ATA is often built into a sma ...

(ATA) or an

IP phone A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet. This is in contrast to a standard phone which uses the traditional public switched telephone network ...

, is sometimes also called ''dial plan''. A pattern 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.

Public switched telephone network (USA)

*''Local numbers'' consist of seven digits within a numbering plan area with a single area code. For overlay numbering plans the area code must dialed before the local telephone number. *''Long distance'' dialing requires the dialing of ''1'', the three-digit area code, and the seven-digit local number. *''International'' numbers of any length are dialing starting with ''011''. Similarly, telephony service operators may provide dialing sequences for special services, such as directory assistance and emergency services.

Private telephone systems

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. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

a dialing plan may specify the addresses of internal extension, as numbers of two, three, or four digits. Dialing telephone numbers of the PSTN often requires the dialing of ''9'' on PBX systems to reach an outside line.

Digit maps

Analog telephone adapter An analog telephone adapter (ATA) is a device for connecting traditional analog telephones, fax machines, and similar customer-premises devices to a digital telephone system or a voice over IP telephony network. An ATA is often built into a sma ...

s, and many other

VoIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...

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,RFC 2705, Media Gateway Control Protocol (MGCP) Version 1.0'', Arango et al. (1999) the specification for the

Media Gateway Control Protocol The Media Gateway Control Protocol (MGCP) is a signaling and call control communication protocol used in voice over IP (VoIP) telecommunication systems. It implements the media gateway control protocol architecture for controlling media gatewa ...

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

References

{{DEFAULTSORT:Dial Plan Telephone numbers