Callback (telecommunications)

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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.

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International calling

A callback, in this sense is a method of making low-cost international calls via a third country, usually the United States, where call charges are considerably lower. One variation of this technology was developed by IDT Corporation in 1991. [1] IDT Corp used a hardware solution that was never widely accepted and ultimately failed and was surpassed by a software solution concurrently developed by Jorge Blanco at MCI Telecommunications for The United Nations Development Programme and their staff Wolfgang Scholtes and Kumar Navaratnum.

In order to use a callback service, a subscriber is allocated a unique number in, for example, the US, which must first be dialled in order to trigger a return call. This is known (in the US) as a Direct Inbound Dialing (DID) number, or in the UK as a Direct Dial-In (DDI) number. Where Caller ID is available, it may be possible to use the same DID number for many different subscribers, as the callback system will be able to recognise each subscriber's registered number.

On hearing a ringing tone, the subscriber simply hangs up and awaits the callback. On receiving this, usually within a few seconds, the customer picks up the phone and dials the required number. This may mean dialling in the North American format, as most callback services are US-based, and callers are effectively calling from the US. For example, a number in Manhattan would be dialled with the trunk code, area code and subscriber's number, as follows:

1 212 xxx xxxx

A call to London in the UK, would require the international access code and country calling code, as follows:

011 44 20 xxxx xxxx

In the North American Numbering Plan, 011 is used as the international access code, but in most countries, 00 is used, in line with International Telecommunication Union's Recommendation E.164.

The cost of making a telephone call via callback consists of two parts, as the caller is effectively paying for an outbound and inbound call at the same time. For example, if a customer from Spain is calling a phone number in Australia, and it costs 8 cents per minute to phone Spain from the US (the callback, which is an incoming call) and 20 cents per minute to phone Australia from the US (the destination call, which is an outgoing call), then the caller will pay a total of 28 US cents a minute. This may still be less expensive than calling directly from Spain to Australia, which is primarily why callbacks are used.

Automated applications

Callback is often automated through the use of web callback or mobile phone applications by companies such as GlobalTel and Jajah, or on Roaming SIMs.

Many countries have banned callback services, on the grounds that they are not licensed or regulated by their governments, and deprive telephone companies in many developing countries of revenue from international calls. People who provide or use callback services have argued that these telephone companies are often state monopolies that charge unjustifiably high prices for international calls. It may also be the only way of making calls to certain countries from others, for example, Israel from other Middle Eastern countries.

Other countries have sought to use technical means to prevent callback, by blocking the inbound and outbound calls made to and from DID numbers, or by disabling touch tone dialing. However, this is also overcome by the use of speed dial numbers, while others use these services by triggering callback via the Internet or SMS.

The use of callback in most developed countries has declined, owing to the liberalization of telecommunication services, which allow more direct access to low-cost international calls, without the need for a time-consuming process like callback. Also, the advent of Voice over Internet Protocol services has allowed many people to make international calls via their computer connected to the Internet, although sound quality can be poorer on slower dial-up connections than on broadband ones.

International callback has been credited with opening global telecom markets because it enabled competition to start up even if regulatory restrictions existed. It was popularized by a 1994 book, "The International CallBack Book" by Gene Retske.

Modem security

A modem allows one computer (the client) to establish a connection to another (the server) by dialing the server's telephone number. This is sometimes viewed as being insecure because there is no authentication of the call originator. One way to increase security is to enforce a modem callback protocol, which usually proceeds as a series of steps:

  1. The client computer calls the server computer.
  2. After a greeting the client identifies itself, usually with a user name.
  3. The server then disconnects the call.
  4. Based upon the user name and a list of users' phone numbers, the server will then establish a second call back to the client computer.
  5. The client computer, expecting this returned call, will then answer and communications between the two computers will proceed normally.

Sometimes callback modem setups can also be used for billback purposes, allowing the originator to avoid lengthy toll charges.

See also

Related Research Articles

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.

<span class="mw-page-title-main">North American Numbering Plan</span> Integrated telephone numbering plan of twenty North American countries

The North American Numbering Plan (NANP) is a telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1 and has the international calling code 1. Some North American countries, most notably Mexico, do not participate in the NANP.

Automatic number identification (ANI) is a feature of a telecommunications network for automatically determining the origination telephone number on toll calls for billing purposes. Automatic number identification was originally created by the American Telephone and Telegraph Company (AT&T) for long distance service in the Bell System, eliminating the need for telephone operators to manually record calls.

Premium-rate telephone numbers are telephone numbers that charge callers higher price rates for select services, including information and entertainment. A portion of the call fees is paid to the service provider, allowing premium calls to be an additional source of revenue for businesses. Tech support, psychic hotlines, and adult chat lines are among the most popular kinds of premium-rate phone services. Other services include directory enquiries, weather forecasts, competitions and ratings televoting. Diplomatic services, such as the US Embassy in London or the UK Embassy in Washington, have also charged premium rates for calls from the general public.

A toll-free telephone number or freephone number is a telephone number that is billed for all arriving calls. For the calling party, a call to a toll-free number from a landline is free of charge. A toll-free number is identified by a dialing prefix similar to an area code. The specific service access varies by country.

Call forwarding, or call diversion, is a telephony feature of all telephone switching systems which redirects a telephone call to another destination, which may be, for example, a mobile or another telephone number where the desired called party is available. Call forwarding was invented by Ernest J. Bonanno. In North America, the forwarded line usually rings once to remind the customer using call forwarding that the call is being redirected. More consistently, the forwarded line indicates its condition by stutter dial tone. Call forwarding typically can redirect incoming calls to any other domestic telephone number, but the owner of the forwarded line must pay any toll charges for forwarded calls. Call forwarding is often enabled by dialing *72 followed by the telephone number to which calls should be forwarded. Once someone answers, call forwarding is in effect. If no one answers or the line is busy, the dialing sequence must be repeated to effect call forwarding. Call forwarding is disabled by dialing *73. This feature requires a subscription from the telephone company. Also available in some areas is Remote Access to call forwarding, which permit the control over call forwarding from telephones other than the subscriber's telephone. VOIP and cable telephone systems also allow call forwarding to be set up and directed via their web portals.

A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reachable by a system of destination code routing. Telephone numbering plans are defined in each of the administrative regions of the public switched telephone network (PSTN) and in private telephone networks.

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.

<span class="mw-page-title-main">Telephone numbers in the United Kingdom</span>

Telephone numbers in the United Kingdom are administered by the Office of Communications (Ofcom). For this purpose, Ofcom established a telephone numbering plan, known as the National Telephone Numbering Plan, which is the system for assigning telephone numbers to subscriber stations.

In Argentina, area codes are two, three, or four digits long. Local customer numbers are six to eight figures long. The total number of digits is ten, for example, phone number (11) 1234-5678 for Buenos Aires is made up of a 2-digit area code number and an 8-digit subscriber's number, while (383) 123-4567 would be an example of a Catamarca number.

Direct inward dialing (DID), also called direct dial-in (DDI) in Europe and Oceania, is a telecommunication service offered by telephone companies to subscribers who operate a private branch exchange (PBX) system. The feature provides service for multiple telephone numbers over one or more analog or digital physical circuits to the PBX, and transmits the dialed telephone number to the PBX so that a PBX extension is directly accessible for an outside caller, possibly by-passing an auto-attendant.

<span class="mw-page-title-main">Telephone numbers in Singapore</span>

Telephone numbers in Singapore, also known as the National Numbering Plan, are regulated by the Info-communications Media Development Authority (IMDA). Due to the small geographical size of Singapore, there are no area or trunk codes; all numbers belong to one numbering area, and thus come in the same 8-digit format. Numbers are categorised based on the first digit, thus providing ten possible categories, of which six are currently in use and the remaining four reserved for future usage.

Area code 246 is the telephone area code in the North American Numbering Plan (NANP) for Barbados. Telecommunication services in Barbados are regulated by the Government of Barbados's telecommunications unit. The number 246 spells BIM on an alpha-numeric telephone keypad, a nickname for the island.

Widespread UK telephone code misconceptions, in particular brought on by the Big Number Change in 2000, have been reported by regulator Ofcom since publication of a report it commissioned in 2004.

<span class="mw-page-title-main">Telephone numbers in Romania</span>

The dialling plan for mobile networks and new landline operators is closed; all subscriber numbers must be dialled in full. For landline numbers starting with 02, the dialling plan used to be open; the trunk digit and area code could be omitted if the caller was in the same area code as the callee. However, starting May 3, 2008, all landline numbers must be dialled in full.

The area code 671 is the local telephone area code of the United States territory of Guam. It was created with the beginning of permissive dialing on July 1, 1997, replacing Guam's previous International Telecommunication Union country code 671 at the end of permissive dialing on July 1, 1998.

The area code 670 is the telephone area code in the North American Numbering Plan (NANP) for the U.S. Commonwealth of the Northern Mariana Islands (CNMI). It was created with the start of permissive dialing on July 1, 1997. With the end of permissive dialing on July 1, 1998, it replaced the previous International Telecommunication Union country code +670, which is now used by East Timor.

National conventions for writing telephone numbers vary by country. While international standards exist in the form of recommendation E.123 by the sector ITU-T of the International Telecommunication Union (ITU), national telephone numbering plans define the format of telephone numbers assigned to telephones and similar communication endpoints.

<span class="mw-page-title-main">Telephone number</span> Sequence of digits assigned to a telephone subscription

A telephone number is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices for data transmission via the public switched telephone network (PSTN) or other public and private networks.

A virtual number, also known as direct inward dialing (DID) or access numbers, is a telephone number without a directly associated telephone line. Usually, these numbers are programmed to forward incoming calls to one of the pre-set telephone numbers, chosen by the client: fixed, mobile or VoIP. A virtual number can work like a gateway between traditional calls (PSTN) and VoIP.

References

  1. ↑ "Budget International Callback Service". GNU. Retrieved 15 July 2015.
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