View source for 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. 

== Description ==

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.

== History ==

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.

== See also ==

* [[Mobile dial code]]
* [[Pat Fleet]] – Prompt voice for most U.S. AT&T implementations of VSC features
* [[Public switched telephone network]]
* [[Signalling System 7]]
* [[Telephony]]

== External links ==

* [https://en.wikipedia.org/wiki/Vertical_service_code Vertical service code] @ Wikipedia


[[Category:Codes]]
[[Category:Telephony]]