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.

These keys were added to provide signals for anticipated data entry purposes in business applications, but found use in Custom Calling Services (CLASS) features installed in electronic switching systems.

Some vertical service codes require dialing of a telephone number after the code sequence.

Telephone numbers are often dialed in conjunction with other signaling code sequences, such as vertical service codes, to invoke special telephone service features.

Most service providers however, allow the caller to block caller ID presentation through the vertical service code *67.

In North America, the NANP uses the *70 star code prefix to suspend call waiting for a dialed call.

Continuous redial, busy number redial, or repeat dial, is a vertical service code (calling feature) that allows callers to automatically redial a busy telephone number until a connection is made.

The general public tends to refer to the service by the telephone feature code, the telephone number it has in their country; for example, in North America this is *69, while in the UK it is called 1471.

In North America, the NANP generally uses the following vertical service codes to control call forwarding:

In North American NANP telephone system, anonymous call rejection (ACR) is a landline calling feature that screens out calls from callers who have blocked their caller ID information.

On a touch tone telephone, the codes are usually initiated with the star key, resulting in the commonly used name star codes.

This led to the addition of the number sign octothorpe asterisk or "star" keys as well as a group of keys for menu selection: A, B, C and D. In the end, the lettered keys were dropped from most phones, and it was many years before the two symbol keys became widely used for vertical service codes such as *67 in the United States of America and Canada to suppress caller ID.

As CLASS was an AT&T trademark, the term vertical service code was adopted by the North American Numbering Plan Administration.

There are also special codes, such as:

This Vertical Service Code, *82, enables calling line identification regardless of subscriber preference, dialed to unblock withheld numbers (private callers) in the U.S. on a per-call basis.

She is also the voice for most "star" services (e.g. last-call return, call blocking, etc.) for AT&T local telephone companies, and the voice heard when making AT&T handled calls through 1-800-CALL-ATT (225-5288) and through international AT&T access numbers such as USADirect.

Priority call, and priority ring are also brand names of calling features which give a distinctive ring to calls from telephone numbers chosen by the subscriber and which require a subscription from their local telephone company.

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. On a touch tone telephone, the codes are usually initiated with the star key, resulting in the commonly used name star codes.

They are used to navigate menus in Touch-Tone systems such as Voice mail, or in Vertical service codes.

Speed calling service allows telephone subscribers to assign one or two digit speed calling codes, by dialing a change speed calling list access code, a feature code, and a new telephone number.

*Vertical service code

1-5-7-1 is the name of a family of calling features in the United Kingdom, for residential and business telephone lines and for mobile telephones, that are provided by BT Group and several other telephone service providers.

Most cell phone services offer voice-mail as a basic feature; many corporate PBXs include versatile internal voice-messaging services, and *98 Vertical service code subscription is available to most individual and small business land line subscribers.

Call whisper, otherwise known as call screening, is a calling feature that often appears on non-geographic telephony systems and hosted inbound call handling software.

Malicious caller identification, activated by Vertical service code Star codes *57, is an upcharge fee subscription service offered by telephone company providers which, when dialed immediately after a malicious call, records meta-data for police follow-up.

Calls are routed according to the set up of calling features within the given system such as Call queues, IVR menus, Hunt groups and Recorded announcements.

Most telephone companies permit callers to withhold the identifying information from calls using the vertical service code *67 that blocks the caller's ID (141 in the UK), but potential victims may be reluctant to answer a call from an ID-blocked number.

In common use, ISDN is often limited to usage to Q.931 and related protocols, which are a set of signaling protocols establishing and breaking circuit-switched connections, and for advanced calling features for the user.

In telecommunication, a virtual call capability, sometimes called a virtual call facility, is a service feature in which:

In telecommunication, a calling-party camp-on is a service feature that enables the telephone exchange to complete an access attempt in spite of temporary unavailability of system transmission or switching facilities required to establish the requested access.