A vertical service code (VSC) is a sequence of digits and the signals

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

() and pound/hash () dialed on a

telephone keypad A telephone keypad is a keypad installed on a push-button telephone or similar telecommunication device for dialing a telephone number. It was standardized when the dual-tone multi-frequency signaling (DTMF) system was developed in the Bell System ...

rotary dial A rotary dial is a component of a telephone or a telephone switchboard that implements a signaling technology in telecommunications known as pulse dialing. It is used when initiating a telephone call to transmit the destination telephone numb ...

to access certain telephone service features. Some vertical service codes require dialing of a

telephone number A telephone number is the address of a Telecommunications, telecommunication endpoint, such as a telephone, in a telephone network, such as the public switched telephone network (PSTN). A telephone number typically consists of a Number, sequ ...

after the code sequence. On a

touch tone Dual-tone multi-frequency (DTMF) signaling is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. DTMF was first developed ...

telephone, the codes are usually initiated with the star key, resulting in the commonly used name ''star codes''. On rotary dial telephones, the star is replaced by dialing ''11''. In

North American North America is a continent in the Northern and Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Caribbean Sea, and to the sou ...

telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is ...

, VSCs were developed by the

American Telephone and Telegraph Company AT&T Corporation, an abbreviation for its former name, the American Telephone and Telegraph Company, was an American telecommunications company that provided voice, video, data, and Internet telecommunications and professional services to busi ...

(AT&T) as Custom Local Area Signaling Services (CLASS or LASS) codes 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 North American Numbering Plan (NANP) is an integrated telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1, World Numbering Zone ...

. The use of ''vertical'' is a somewhat dated reference to older switching methods and the fact that these services can only be accessed by a telephone subscriber, going up (''vertically'') inside the local central office instead of out (''horizontally'') to another telephone company.

Feature definitions

The following are the vertical service codes generally recommended by the

North American Numbering Plan Administrator The North American Numbering Plan (NANP) is an integrated telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1, World Numbering Zone ...

for use in the NANP territories. Not all of these services are available in all areas, and some are only available on

landline A landline is a physical telephone connection that uses metal wires or optical fiber from the subscriber's premises to the network, allowing multiple phones to operate simultaneously on the same phone number. It is also referred to as plain old ...

telephones or

Mobile phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This rad ...

s. Local Area Signalling Services (LASS) and Custom Calling Feature Control Codes:

References

External links

ETSI Supplementary service codes
{{FS1037C Calling features North American Numbering Plan Telephone numbers in Canada

Feature definitions

See also

References

External links