
1) Calling need, at times 2) Calling trio 3) Certain numerical prefix 4) Certain three-digit number 5) Common three before seven 6) Customer file datum 7) Customer file entry 8) Customer-file entry 9) Dialing prefix 10) Directory assistance info 11) Exchange preceder 12) Figures out at the beginning
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https://www.crosswordclues.com/clue/area-code

(from the article `telephone and telephone system`) ...the goal of providing direct long-distance service throughout the nation. Accordingly, in 1945 AT&T standardized the currently universal system of ...
Found on
http://www.britannica.com/eb/a-z/a/97

Area Code is colloquial term for a three or more digit number identifying one geographic area of a country providing for Direct Distance Dialling on the public telephone network system of that country. This entire system of numbers is under the umbrella of Country Code 01 in the World Numbering Plan of the CCITT.
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http://www.probertencyclopaedia.com/browse/GA.HTM

[
n] - a number usually of 3 digits assigned to a telephone area as in the US and Canada
Found on
http://www.webdictionary.co.uk/definition.php?query=area%20code
noun a number usually of 3 digits assigned to a telephone area as in the United States and Canada
Found on
https://www.encyclo.co.uk/local/20974

a three-digit code that identifies one of the telephone areas into which the U.S. and certain other countries are divided and that precedes the local telephone number when dialing a call between areas.
Found on
https://www.infoplease.com/dictionary/area-code
No exact match found.