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Vertical service code
A vertical service code (VSC) is a special code dialed prior to (or instead of) a telephone number that engages some type of special telephone service or feature. Typically preceded with an asterisk, or
* (star), key on the touch tone keypad and colloquially referred to as star codes, most are two digits in length; as more services are developed, those that use ''2'' or ''3'' as the first digit are sometimes three digits in length.
In North American telephony, VSCs were developed by AT&T Corp. as Custom Local Area Signaling Services or CLASS codes (sometimes LASS) in the 1960s and 70s. Their use became ubiquitous throughout the 1990s and eventually became a recognized standard. As ''CLASS'' was an AT&T trademark, the term "vertical service code" was adopted by the North American Numbering Plan Administration. The use of the word "vertical" is a somewhat dated reference to older switching methods and the fact that these services can only be accessed by a local telephone subscriber, going up (or vertically) inside the local central office instead of out (or horizontally) to another telephone company.
== List of vertical service codes ==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Vertical service code」の詳細全文を読む
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