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  2. 555 (telephone number) - Wikipedia

    en.wikipedia.org/wiki/555_(telephone_number)

    The telephone number prefix 555 is a central office code in the North American Numbering Plan, used as the leading part of a group of 10,000 telephone numbers, 555-...., in each numbering plan area (NPA) (area code). It has traditionally been used only for the provision of directory assistance, when dialing NPA-555-1212.

  3. List of North American Numbering Plan area codes - Wikipedia

    en.wikipedia.org/wiki/List_of_North_American...

    1-NPA-555-01XX is used for fictional telephone numbers; ... but was changed to avoid confusion with central office codes [4] 2021: overlaid by 474; 640:

  4. Telephone exchange names - Wikipedia

    en.wikipedia.org/wiki/Telephone_exchange_names

    Telephone numbers listed in 1920 in New York City having three-letter exchange prefixes. In the United States, the most-populous cities, such as New York City, Philadelphia, Boston, and Chicago, initially implemented dial service with telephone numbers consisting of three letters and four digits (3L-4N) according to a system developed by W. G. Blauvelt of AT&T in 1917. [1]

  5. North American Numbering Plan - Wikipedia

    en.wikipedia.org/wiki/North_American_Numbering_Plan

    For example, 234 235-5678 is a valid telephone number; with area code 234, central office prefix (exchange) 235, and line number 5678. The number 234 911-5678 is invalid, because the central office code must not be in the form N11. 314 159-2653 is invalid, because the office code must not begin with 1.

  6. Interchangeable NPA and central office codes - Wikipedia

    en.wikipedia.org/wiki/Interchangeable_NPA_and...

    The solution for expanding the numbering pool within an NPA was to remove the restriction posed by not using 0 and 1 in the middle position of central office codes. This made central office codes interchangeable. An interchangeable NPA code and an interchangeable central office code is a code that permits any of the ten numerals in the middle ...

  7. Fictitious telephone number - Wikipedia

    en.wikipedia.org/wiki/Fictitious_telephone_number

    So-called "interchangeable central office codes" with 0's or 1's in the second or third positions ... Hungarian taxi company Tele5 Taxi uses 555-5555 as a vanity ...

  8. Telephone numbers in Canada - Wikipedia

    en.wikipedia.org/wiki/Telephone_numbers_in_Canada

    Telephone numbers in Canada follow the fixed-length format of the North American Numbering Plan (NANP) of a three-digit area code, a three-digit central office code (or exchange code), and a four-digit station or line code. This is represented as NPA NXX XXXX. [1]

  9. List of future North American area codes - Wikipedia

    en.wikipedia.org/wiki/List_of_future_North...

    This is a list of future area codes in the North American Numbering Plan (NANP) that are in the planning stages for relief of central office code exhaustion in the given numbering plan areas (NPAs). The dates are subject to change during implementation as published in the official NANP Administrator Planning Letters.