Abbreviated dialing

Abbreviated dialing is the use of a very short digit sequence to reach specific telephone numbers, such as those of public services. The purpose of such numbers is to be universal, short, and easy to remember. Typically they are two or three digits.

Carriers refer to the shortened number sequences as abbreviated dialing codes (ADCs). Unlike SMS shortcodes, they are generally not automatically synchronized across carriers. ADCs are provisioned separately for mobile networks versus landline networks.

The most commonly known examples are emergency telephone numbers such as 9-9-9, 1-1-2 and 9-1-1. Other services may also be available through abbreviated dialing numbers, such as the other of the eight N11 codes of the North American Numbering Plan (NANP) besides 9-1-1. State highway departments in recent years have used abbreviated dialing codes to allow drivers to obtain information about road conditions or to reach the state highway patrol. Examples are *55 in Missouri and Oklahoma, or *FHP which connects to the Florida Highway Patrol.

For text messaging, the technical equivalent is a short code; however these are rented by their private users rather than being universal and for public services.

Vertical service codes may also be considered as abbreviated dialing, though these prefix the special touch-tone characters * and # (or often 11 for pulse dialing) instead of using only numerals. Most are used to access calling features rather than a called party, and some are specific to each telephone company. Some are used only locally or regionally (such as *FHP (*347) to reach the Florida Highway Patrol); other codes as short as one numeral (like *1) are used to report breaking news or traffic to the newsrooms of local news radio or TV stations.

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