Vertical service code

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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 the 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) 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 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[edit]

North America[edit]

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 code Service definition
*30 Not Supported Cancel forwarding[note 1]
*31 Not Supported Automatic forwarding[note 1]
*32 Not Supported Notify[note 1]
*51 1151 Intercom ring 1 (short short)[note 2]
*52 1152 Intercom ring 2 (short short long)[note 2]
*53 1153 Intercom ring 3 (short long short)[note 2]
*54 1154 Extension hold[note 2]
*57 1157 Malicious caller identification
*60 1160 Call blocking
*61 1161 Priority call
*62 1162 Selective call acceptance
*63 1163 Selective call forwarding
*65 1165 Caller ID
*66 1166 Continuous redial
*67 1167 Number display blocking (per call)[note 3]
*68 1168 Activate call forwarding on busy
*69 1169 Last-call return (incoming)
*70 1170 Call waiting disable[note 3]
*71 1171 Conditional forward: No answer[note 4]
*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[note 5]
*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)[note 3][note 6]
*83 1183 Selective call forwarding disable
*85 1185 Caller ID disable
*86 1186 Continuous redial cancel[note 7]
Voicemail[note 8]
*87 1187 Anonymous call rejection disable[note 5]
*88 1188 Deactivate call forwarding on busy
*89 1189 Last-call return cancel[note 7]
*90 1190 Conditional forward: Busy line
*92 1192 Conditional forward: No answer
*94 1192 Directed call pickup
*98 1198
Not Supported
Blind Transfer[note 9][4]


  1. ^ a b c Code used for Cellular One service
  2. ^ a b c d Found in Pac Bell territory. Intercom ring causes a distinctive ring to be generated on the current line. Hold keeps a call connected until another extension is picked up.
  3. ^ a b c Applied once before each call. Caller ID to 8xx NPA numbers and 911 cannot be blocked.
  4. ^ Used by certain carriers (like Verizon Wireless), but this use is non-standard.
  5. ^ a b ACR blocks calls from those who blocked Caller ID (used in C&P territory, for instance)
  6. ^ Has been mandated to be the nationwide code for, "Send CLID info regardless of the default setting on this phone line."
  7. ^ a b Cancels further return attempts
  8. ^ On the FiOS networks owned by Frontier Communications and Verizon dialing *86 connects to the subscriber to their phone's voicemail system.
  9. ^ When using an OBi Analog telephone adapter in conjunction with a supported service such as Google Voice dialing *98 followed by the telephone number will transfer the call in an unsupervised mode i.e. the transferring party will hear three short tone bursts and then be automatically disconnected from the call. This VSC is not supported by Google Voice on its Web site or app.

See also[edit]


  1. ^ a b "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. 
  4. ^ OBi Feature Star Codes Directory

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