Vertical service code

A vertical service code (VSC) is a sequence of digits and the signals star (*) and number sign (#) dialed on a telephone keypad or rotary dial to enable or disable certain telephony service features.[1] Some vertical service codes require dialing of a telephone number after the code sequence. On a touch tone 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 telephony, VSCs were developed by AT&T Corp. 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 use of 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 (vertically) inside the local central office instead of out (horizontally) to another telephone company.

Feature definitions

North America

The following are the vertical service codes generally recommended by the North American Numbering Plan Administration for use in the NANP territories. Not all of these services are available in all areas, and some are only available to landline or cellular telephones.

Local Area Signalling Services (LASS) and Custom Calling Feature Control Codes:[2][1][3]

Vertical service codeService definition
*51 1151 Who called me. Provides the directory number, date and time of unanswered calls
*52 1152 Call Hold (Single Line Variety Package). Permits the call to be picked up at another station.
*53 1153 Distinctive Ring B. Allows a subscriber to alert a specific party distinctively.
*54 1154 Distinctive Ring C. Allows a subscriber to alert a specific party distinctively.
*57 1157 Call trace
*60 1160 Call blocking
*61 1161 Priority call
*62 1162 Selective call waiting
*63 1163 Selective call forwarding
*65 1165 Calling number delivery activation
*66 1166 Continuous redial
*67 1167 Calling number delivery blocking
*68 1168 Activate call forwarding on busy
*69 1169 Last-call return (incoming)
*70 1170 Call waiting disable
*71 1171 Usage sensitive three-way call
*72 1172 Unconditional forward: All calls
*73 1173 Call forward: Cancel
*74 1174 Speed calling (8 numbers)
*75 1175 Speed calling (30 numbers)
*77 1177 Anonymous call rejection activation
*78 1178 Do not disturb
*79 1179 Do not disturb disable
*80 1180 Call blocking disable
*81 1181 Priority call disable
*82 1182 Caller ID (per call)
*83 1183 Selective call forwarding disable
*85 1185 Caller ID disable
*86 1186 Continuous redial cancel
*87 1187 Anonymous call rejection deactivation
*88 1188 Deactivate call forwarding on busy
*89 1189 Last-call return cancel
*90 1190 Conditional forward: Busy line
*92 1192 Conditional forward: No answer
*94 1194 Directed call pickup

See also


  1. "Vertical Service Codes – Code Definitions". Neustar. Retrieved 2013-03-18.
  2. voyager (1995-04-15). Erik Bloodaxe (ed.). "The #hack FAQ". Phrack Magazine. p. 7. Retrieved 2013-03-18.
  3. "Vertical Service Codes – Code Assignments". Neustar. Retrieved 2013-03-18.

 This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C".

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