page_title: Telephone number
section_title: Alphanumeric telephone numbers
hierarchical_section_title: Telephone number / History / United States / Alphanumeric telephone numbers
caption_attribution_description: English: Star Hair Stylists, 1399 Queen St. W., Toronto, with an exterior sign showing the shop's telephone number in the old two-letters plus five-digits format
context_page_description: A telephone number is a sequence of digits assigned to a fixed-line telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network or other public and private networks.
  A telephone number serves as an address for switching telephone calls using a system of destination code routing. Telephone numbers are entered or dialed by a calling party on the originating telephone set, which transmits the sequence of digits in the process of signaling to a telephone exchange. The exchange completes the call either to another locally connected subscriber or via the PSTN to the called party. Telephone numbers are assigned within the framework of a national or regional telephone numbering plan to subscribers by telephone service operators, which may be commercial entities, state-controlled administrations, or other telecommunication industry associations.
  Telephone numbers were first used in 1879 in Lowell, Massachusetts, when they replaced the request for subscriber names by callers connecting to the switchboard operator.
context_section_description: The North American Numbering Plan of 1947 prescribed a format of telephone numbers that included two leading letters of the name of the central office to which each telephone was connected. This continued the practice already in place by many telephone companies for decades. Traditionally, these names were often the names of towns, villages, or were other locally significant names. Communities that required more than one central office may have used other names for each central office, such as Main, East, West, Central, or the names of local districts. Names were convenient to use and reduced errors when telephone numbers were exchanged verbally between subscribers and operators. When subscribers could dial themselves, the initial letters of the names were converted to digits as displayed on the rotary dial. Thus, telephone numbers contained one, two, or even three letters followed by up to five numerals. Such numbering plans are called 2L-4N, or simply 2–4, for example, as shown in the photo of a telephone dial of 1939 (right). In this example, LAkewood 2697 indicates that a subscriber dialed the letters L and A, then the digits 2, 6, 9, and 7 to reach this telephone in Lakewood, NJ (USA). The leading letters were typically bolded in print.
  In December 1930, New York City became the first city in the United States to adopt the two-letter and five-number format (2L-5N), which became the standard after World War II, when the Bell System administration designed the North American Numbering Plan to prepare the United States and Canada for Direct Distance Dialing (DDD), and began to convert all central offices to this format. This process was complete by the early 1960s, when a new numbering plan, often call all number calling (ANC) became the standard in North America.
caption: 2008 photo shows a hairdressing shop in Toronto with an exterior sign showing the shop's telephone number in the old two-letters plus five-digits format.
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