词条 | List of original NANP area codes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
释义 |
This is the list of original North American Numbering Plan area codes of 86 plan areas as defined by AT&T in 1947. In preparation for direct distance dialing, AT&T and the Bell System developed the North American Numbering Plan in the 1940s. The plan divided the United States and Canada into numbering plan areas (NPAs) and assigned a three-digit dialing prefix to each. Over the course of the decade following introduction of these routing codes, local subscriber numbers were standardized to seven digits. This included a three-digit central office prefix, dialed as the first two letters of the local central office name and one digit, and the four-digit subscriber station number.[1] The first digit of the area code was never 0 or 1, as a single leading pulse (1) was ignored by most switching equipment, and 0 could be confused with requests for an operator or the long-distance desk.[1] The original numbering plan defined the second digit of all area codes as either 0 or 1, to distinguish them from the central office codes, which always used a letter in the middle position, as letters were mapped on the dial only to digits 2 through 9. Area codes with the middle digit 0 were assigned to numbering plan areas that covered an entire state or province, while jurisdictions with multiple plan areas received area codes having 1 as the second digit.[2] No codes of the form N00, N10 or N11 occurred in the original area code allocation, where N is 2 through 9. The series N00 was used for non-geographic numbers, starting with intrastate toll-free 800-numbers in 1966.[3] N10 numbers were originally teletypewriter exchanges and N11 remains reserved for information and emergency numbers. No codes were originally assigned to territories of the United States, including Alaska and Hawaii.[4] Initially, the numbering plan area codes were used in Nationwide Operator Toll Dialing by long-distance operators for placing trunk calls.[5] Preparations proceeded for end-customer direct distance dialing (DDD) and while the first customer-dialed call using an area code was placed on November 10, 1951, from Englewood, New Jersey, to Alameda, California,[6] it took until the 1960s until direct distance dialing was commonplace in most cities.{{citation needed|date = September 2017}}
See also
References1. ^1 AT&T (1955), Notes on Nationwide Dialing, pp.3 {{DEFAULTSORT:Original NANP area codes}}2. ^{{cite web|url=https://www.theatlantic.com/technology/archive/2014/02/our-numbered-days-the-evolution-of-the-area-code/283803/ |title=Our Numbered Days: The Evolution of the Area Code |publisher=The Atlantic |date=2014-02-13 |accessdate=2016-08-28}} 3. ^{{cite web|url=http://www.atlantatelephonehistory.info/part4.html |title=Atlanta Telephone History |website=Atlantatelephonehistory.info |date=1968-06-29 |accessdate=2016-08-28}} 4. ^{{cite web|url=http://www.lincmad.com/map1947.html |title=LincMad's 1947 Area Code Map |website=Lincmad.com |date= |accessdate=2016-08-28}} 5. ^Ralph Mabbs, Nation-Wide Operator Toll Dialing—the Coming Way, Bell Telephone Magazine 1947 p.180 6. ^{{cite web|url=http://www.corp.att.com/attlabs/reputation/timeline/51trans.html |title=AT&T Labs Fosters Innovative Technology | AT&T Labs |website=Corp.att.com |date= |accessdate=2016-08-28}} 7 : North American Numbering Plan|Telephone numbers in the United States|Telephone numbers in Canada|Area codes in Canada|Telecommunications-related introductions in 1947|Canada communications-related lists|United States communications-related lists |
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