telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

, 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 numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reach ...

. Dial plans in the

public switched telephone network The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists o ...

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) or FXS gateway 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 telephone network. An ATA is often ...

(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 be 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 dialed 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, and end-user telephones may use variable-length or fixed-length dial plans. In private branch exchanges in the

U.S. The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and a federal capital district, Washington, D.C. The 48 contiguous ...

a dialing plan may specify the addresses of internal extensions, typically as numbers of two, three, or four digits. Dialing from a PBX telephone is usually by default to internal numbers, i.e. for calls within the PBX, so that reaching PSTN numbers often requires dialing a special prefix, e.g. a ''9'', before the PSTN number.

Digit maps

Analog telephone adapter An analog telephone adapter (ATA) or FXS gateway 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 telephone network. An ATA is often ...

s, and many other

VoIP Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

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 telecommunication protocol for signaling and call control in hybrid voice over IP (VoIP) and traditional telecommunication systems. It implements the media gateway control protocol architecture f ...

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

References

{{DEFAULTSORT:Dial Plan Telephone numbers