Vertical service code

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[1]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[edit]

North America[edit]

The following are the VSCs generally used in the North American Numbering Plan. Not all of these services are available in all areas, and some are only available to landline or cellular telephones. Some require additional services be purchased from the telephone company to use them.

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

Service Tone Pulse/rotary
Cancel forwarding[note 1] *30 Not Supported
Automatic forwarding[note 1] *31 Not Supported
Notify[note 1] *32 Not Supported
Intercom ring 1 (short short)[note 2] *51 1151
Intercom ring 2 (short short long)[note 2] *52 1152
Intercom ring 3 (short long short)[note 2] *53 1153
Extension hold[note 2] *54 1154
Malicious caller identification *57 1157
Call blocking *60 1160
Priority call *61 1161
Selective call acceptance *62 1162
Selective call forwarding *63 1163
Caller ID *65 1165
Continuous redial *66 1166
Number display blocking (per call)[note 3] *67 1167
Activate call forwarding on busy *68 1168
Last-call return (incoming) *69 1169
Call waiting disable[note 3] *70 1170
Conditional forward: No answer[note 4] *71 1171
Usage sensitive three-way call *71 1171
Unconditional forward: All calls *72 1172
Call forward: Cancel *73 1173
Speed calling (8 numbers) *74 1174
Speed calling (30 numbers) *75 1175
Anonymous call rejection[note 5] *77 1177
Do not disturb *78 1178
Do not disturb disable *79 1179
Call blocking disable *80 1180
Priority call disable *81 1181
Caller ID (per call)[note 3][note 6] *82 1182
Selective call forwarding disable *83 1183
Caller ID disable *85 1185
Continuous redial cancel[note 7]
Voicemail[note 8]
*86 1186
Anonymous call rejection disable[note 5] *87 1187
Deactivate call forwarding on busy *88 1188
Last-call return cancel[note 7] *89 1189
Conditional forward: Busy line *90 1190
Conditional forward: No answer *92 1192
Directed call pickup *94 1192
Blind Transfer[note 9][4]
*98 1198
Not Supported

United Kingdom[edit]

Main article: 1-5-7-1


  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".