Ringback number

Last updated October 21, 2022

A ringback number is a telephone number for a telephone line that automatically calls the line that the call was placed from, after the caller has hung up. The typical use of this facility is by telephone company technicians for testing a new installation or for trouble-shooting.^[1]

Operation

Ringback testing is an acceptance testing procedure conducted by telephone installers to verify the quality of customer premises wiring to prevent network damage from faulty equipment or installation. The test consists of calling a reverting calling telephone number (ringback number) or a vertical service code with a standard telephone. Upon answering the call, the exchange plays a unique signal tone as a signal for the installer to hangup the telephone. The exchange then places a reverting call to the originating line, causing the telephone to ring. When answered, the exchange plays a verification tone. The verification tone is issued so that telephone subscribers cannot easily use the ringback system as an intercom between multiple stations in a residence on the same line by taking the stations off-hook.^[2]

Ringback numbers are typically not listed or communicated to subscribers.^[2]

Coin telephones

Narcotics trafficking and other criminal activity can use payphones to conduct crimes anonymously, so many payphones are not equipped with a ringer at all, or a quiet "chirper" solid state speaker and designated "No Incoming Calls". All payphones in the United States must be assigned a telephone number in order to make calls, some can ring or chirp if that number is called. Many customer-owned coin-operated telephones (COCOT) answer the phone at first ring with a built in modem which can be accessed by technicians to report conditions and program function parameters, one programmable function is the number of rings until the modem answers, another is whether to impose an additional charge for incoming calls or even accept no incoming calls at all. Where a payphone does not have any number listed on the unit, the number can be discovered from that phone by calling an automatic number announcement circuit (ANAC) service or a telephone with caller ID. TelCo owned payphones are generally on dedicated payphone lines which respond to special tones and Custom Local Area Signaling Services codes such as *5055 for ringback.

Examples

Some ringback numbers are local or regional in scope, while others are larger in scope. Every telephone company determines its own ringback numbers for each individual central office. Under the North American Numbering Plan, most North American area codes reserve telephone numbers beginning with 958 and 959 for internal testing. Some companies also reserve 999 for test exchanges. Numbers within these test exchange block ranges are used for various types of local and long-distance testing; generally, this block includes a ringback number (to test the ringer when installing telephone sets) and a loop around (which connects a call to another inbound call to the same or another test number). Ringback numbers may appear in the 958 exchange, but there is no requirement that they reside there.

Some large telephone companies have toll-free numbers set up for ringback. In most cases, these numbers remain undisclosed to prevent abuse. Some companies change their ringback number every month to maintain secrecy. Some carriers (such as Bell Canada) have been known to disable all payphone calls to 958 or 959 test lines.

4101 was formerly valid on some mechanical switching systems to allow a call to the other party on a two-party line. Like 4104 (repair, long replaced by 611 in most cities), it was once a standard number in many areas but has disappeared as this equipment (and the party line service itself) has been decommissioned.

In the 1970s and early 1980s, 1199011 was a number that when called would result in another dial tone. Afterwards, if the phone was hung up and then quickly picked up again in less than approximately 1/2 second (ie: a hook flash), a steady tone would then be heard (different then a regular dial tone). Hanging up the phone after this would result in a ring back. When the ring back was answered, the ring back process could be repeated by hanging up and lifting up the phone quickly again, and then hanging up.

Most other numbers listed for ringback are specific to one exchange or one telco; available lists tend to be outdated and unreliable. Many former test numbers (such as 320 and 999 in Bell Canada territory) have been reclaimed for use as standard landline or mobile exchange prefixes, with the test codes moved (usually) to the 958 exchange.

Related Research Articles

An automatic number announcement circuit (ANAC) is a component of a central office of a telephone company that provides a service to installation and service technicians to determine the telephone number of a telephone line. The facility has a telephone number that may be called to listen to an automatic announcement that includes the caller's telephone number. The ANAC facility is useful primarily during the installation of landline telephones to quickly identify one of multiple wire pairs in a bundle or at a termination point.

A telephone switchboard was a device used to connect circuits of telephones to establish telephone calls between users or other switchboards, throughout the 20th century. The switchboard was an essential component of a manual telephone exchange, and was operated by switchboard operators who used electrical cords or switches to establish the connections.

Phreaking is a slang term coined to describe the activity of a culture of people who study, experiment with, or explore telecommunication systems, such as equipment and systems connected to public telephone networks. The term phreak is a sensational spelling of the word freak with the ph- from phone, and may also refer to the use of various audio frequencies to manipulate a phone system. Phreak, phreaker, or phone phreak are names used for and by individuals who participate in phreaking.

A dial tone is a telephony signal sent by a telephone exchange or private branch exchange (PBX) to a terminating device, such as a telephone, when an off-hook condition is detected. It indicates that the exchange is working and is ready to initiate a telephone call. The tone stops when the first dialed digit is recognized. If no digits are forthcoming, the partial dial procedure is invoked, often eliciting a special information tone and an intercept message, followed by the off-hook tone, requiring the caller to hang up and redial.

Caller identification is a telephone service, available in analog and digital telephone systems, including voice over IP (VoIP), that transmits a caller's telephone number to the called party's telephone equipment when the call is being set up. The caller ID service may include the transmission of a name associated with the calling telephone number, in a service called Calling Name Presentation (CNAM). The service was first defined in 1993 in International Telecommunication Union—Telecommunication Standardization Sector (ITU-T) Recommendation Q.731.3.

A blue box is an electronic device that produces tones used to generate the in-band signaling tones formerly used within the North American long-distance telephone network to send line status and called number information over voice circuits. This allowed the user, referred to as a "phreaker", to surreptitiously place long-distance calls that would be billed to another number or dismissed entirely as an incomplete call. A number of similar "color boxes" were also created to control other aspects of the phone network.

Wardialing is a technique to automatically scan a list of telephone numbers, usually dialing every number in a local area code to search for modems, computers, bulletin board systems and fax machines. Hackers use the resulting lists for various purposes: hobbyists for exploration, and crackers—malicious hackers who specialize in breaching computer security—for guessing user accounts, or locating modems that might provide an entry-point into computer or other electronic systems. It may also be used by security personnel, for example, to detect unauthorized devices, such as modems or faxes, on a company's telephone network.

A ringtone, ring tone or ring is the sound made by a telephone to indicate an incoming call. Originally referring to and made by the electromechanical striking of bells, the term now refers to any sound on any device alerting of a new incoming call—up to and including recordings of original telephone bells.

<span class="mw-page-title-main">Answering machine</span> Telephone answering device

An answering machine, answerphone or message machine, also known as telephone messaging machine in the UK and some Commonwealth countries, ansaphone or ansafone, or telephone answering device (TAD), was used for answering telephones and recording callers' messages. If a phone rings a number of times predetermined by the phone's owner, and nobody is present to answer the incoming call, the answering machine will activate and play either a generic announcement or the voice of the person being called announcing that nobody is able to come to the phone at the moment. Following the announcement is a beeping tone which prompts the caller to record a message after the tone concludes.

<span class="mw-page-title-main">Telephone call</span> Connection between two or more people over a telephone network

A telephone call is a connection over a telephone network between the called party and the calling party.

Call waiting is a telephone service where a subscriber can accept a second incoming telephone call by placing an in-progress call on hold—and may also switch between calls. With some providers it can be combined with additional features such as conferencing, call forwarding, and caller ID. Call waiting is intended to alleviate the need to have more than one telephone line or number for voice communications.

In telecommunications, a callback or call-back occurs when the originator of a call is immediately called back in a second call as a response.

Phone fraud, or more generally communications fraud, is the use of telecommunications products or services with the intention of illegally acquiring money from, or failing to pay, a telecommunication company or its customers.

The New Zealand telephone numbering plan describes the allocation of telephone numbers in New Zealand and the Pitcairn Islands.

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. The family is named after the telephone number 1571, the special service number that is used to access it. Call Minder is the name of BT's highest level of 1571 service.

Ringing is a telecommunication signal that causes a bell or other device to alert a telephone subscriber to an incoming telephone call. Historically, this entailed sending a high-voltage alternating current over the telephone line to a customer station which contained an electromagnetic bell. It is therefore also commonly referred to as power ringing, to distinguish it from another signal, audible ringing, or ringing tone, which is sent to the originating caller to indicate that the destination telephone is in fact ringing.

Telephone number verification services are online services used to establish whether a given telephone number is in service. They may include a form of Turing test to further determine if a human answers or answering equipment such as a modem, fax, voice mMail or answering machine.

An automatic dialer is an electronic device or software that automatically dials telephone numbers. Once the call has been answered, the autodialer either plays a recorded message or connects the call to a live person.

In landline telephony, a plant test number or exchange is a number or group of numbers reserved for use by telephone installers or other workers to perform routine tests on an individual telephone line. Most are unlisted numbers.

The Panel Machine Switching System is a type of automatic telephone exchange for urban service that was used in the Bell System in the United States for seven decades. The first semi-mechanical types of this design were installed in 1915 in Newark, New Jersey, and the last were retired in the same city in 1983.

References

↑ Petersen, Julie (2002). The telecommunications illustrated dictionary. Petersen, Julie K. (2nd ed.). Boca Raton, Fla.: CRC Press. p. 804. ISBN 084931173X. OCLC 51169186.
1 2 50 FR 29391 Federal Register,50 (139), (19 July 1985). Seen 03 February 2021.

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[1] Petersen, Julie (2002). The telecommunications illustrated dictionary. Petersen, Julie K. (2nd ed.). Boca Raton, Fla.: CRC Press. p. 804. ISBN 084931173X. OCLC 51169186.

[:0-2] 1 2 50 FR 29391 Federal Register,50 (139), (19 July 1985). Seen 03 February 2021.

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