Telephone Numbers in The United States - Alphabetic Mnemonic System

Alphabetic Mnemonic System

Telephone dials and usage in the NANP service areas maintain the tradition of alphabetic dialing. On most US and Canadian telephones, three letters appear on each number button from 2 through 9 (as standardized much later by ISO 9995-8 and, in Europe, E.161). This accommodates 24 letters. Historically, the letters Q and Z were omitted, though on some modern telephones they are added, so that the alphabet is apportioned as follows:

2 = ABC 3 = DEF 4 = GHI 5 = JKL 6 = MNO 7 = PRS or PQRS 8 = TUV 9 = WXY or WYZ or WXYZ

No letters are typically mapped to the 1 or 0 keys, although some corporate voicemail systems use Q and Z as 1, and some old telephones assigned the Z to the digit 0.

Originally, this scheme was used as a mnemonic device for telephone number prefixes. When telephone numbers in the US were standardized in the mid-20th century to seven digits, the first two digits of the exchange prefix were expressed as letters rather than numbers, using the name of the telephone exchange. Before World War II, the large cities used three letters and four or five numbers; in most cities with customer dialing, phone numbers had only six digits (2L-4N). The prefix was a name, and the first two or three letters (usually shown in capitals) of the name were dialed. Later, the third letter (where previously used) was replaced by a number, or an extra number was added; this generally happened after World War II, although New York City did this in 1930. Thus, the famous Glenn Miller tune "PEnnsylvania 6-5000" refers to a telephone number +1 (212) 736-5000, the number of the Hotel Pennsylvania, which still bears the same number today. Similarly, the classic film "BUtterfield 8" is set in the East Side of Manhattan between roughly 64th and 86th Streets, where the telephone prefixes include 288. This is why, in some works of fiction, phone numbers will begin with "KLondike 5" or "KLamath 5", which translates to 555, an exchange that is reserved for information numbers in most areas.

The letter system was phased out, beginning before 1965 (though it persisted ten years later in some places, and was included in Bell of Pennsylvania directories until 1983), but alphabetic dialing remains as a commercial mnemonic gimmick, particularly for toll-free numbers. For example, one can dial 1-800-FLOWERS to send flowers to someone, or 1-800-DENTIST to find a local dentist. Sometimes, longer phonewords are used — for example one might be invited to give money to a public radio station by dialing 1-866-KPBS-GIVE. The "number" is 8 digits long, but only the first seven need be dialed. If an eighth (or more) digit is dialed, the switching system will ignore it. Mobile and VoIP users may need to manually drop any numbers past the seventh digit as some mobile switching systems will not automatically ignore them, resulting in a failed call. Also, some users of smartphones devices can have difficulty dialing phonewords, as some of those devices do not have the apportioned letters on the keys used for dialing. This can be avoided by accompanying the use of phonewords with the actual numeric phone number, allowing users of such smartphones to dial using the numeric phone number. Some smartphones permit dialing phonewords by holding down a special function key, such as ALT in the case of the BlackBerry, while pressing another key on the qwerty pad.

In addition to commercial uses, alphabetic dialing has occasionally influenced the choice of regional area codes in the United States. For example, when area 423 (East Tennessee) was split in 1999, the region surrounding Knoxville was assigned area code 865, chosen to represent the word "VOL"—short for "Volunteers", the nickname of athletic teams at the University of Tennessee.

The state of Nevada has previously attempted to obtain area code 777 (lucky 7's), but was unable to secure it.