Vertical service code explained

A vertical service code (VSC) is a sequence of digits and the signals star (*) and pound/hash (#) dialed on a telephone keypad or rotary dial to access certain telephone service features. 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 the American Telephone and Telegraph Company (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 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 for use in the NANP territories. Not all of these services are available in all areas, and some are only available on landline telephones or Mobile phones.

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

Vertical service code		Service definition	Australia	France	Israel	Japan	UK
Tone dialing	Pulse dialing
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 (Malicious caller identification)
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	1831 #31#^[4] ^[5]				141 #31#^[6]
68	1168	Activate call forwarding on busy
69	1169	Last-call return (incoming)	69 HFC *10#^[7] ^[8]	3131	42	1361 1363^[9]	1471^[10]
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)	31#/1832^[11]				1470
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
272		Wireless Priority Service

See also

• Mobile dial code
• Pat Fleet – Prompt voice for most U.S. AT&T implementations of VSC features
• Public switched telephone network
• Short code

External links

• ETSI Supplementary service codes

Notes and References

1. The #hack FAQ. voyager. Erik Bloodaxe. Phrack Magazine. 7. 1995-04-15. 2013-03-18.
2. Web site: Vertical Service Codes – Code Definitions. North American Numbering Plan Administrator. NationalNANPA.com. 2022-07-30.
3. Web site: Vertical Service Codes – Code Assignments. Neustar. NANPA.com. 2013-03-18.
4. 1831 on landlines, or #31# from a mobile
5. Web site: HOW TO: block your number when calling someone. Telstra Exchange. Telstra. 28 May 2017.
6. 141 on landlines and #31# on mobiles
7. • 10# for Telstra services "Telstra Home Phones and Plans – Call Return"
8. • 69 on Optus HFC Telephony network. "Optus Personal – Using Call Return" This only allows one to return the last unanswered call, and can cost 35 cents per use.
9. 1361 to get number, 1363 to call back. Web site: NewsRelease . NTT East . June 20, 2013. Web site: Number OSIRASE 136 . NTT West . June 20, 2013.
10. After dialing 1471, the caller can press "3" to automatically return the call. Previously free, since August 2004 the return call service incurs a charge.
11. 1832 on landlines, or *31# from a mobile