Callback (telecommunications)
Encyclopedia
In telecommunications, a callback (also written as call-back) occurs when the originator of a call is immediately called back in a second call as a response.
, where call charges are considerably lower.
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 America
n 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.
or mobile phone applications by companies such as GlobalTel
, Alliance Communication, Save a Minute, Call2.com
, Jajah
or on Roaming SIM
s.
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.
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:
Sometimes callback modem setups can also be used for billback
purposes, allowing the originator to avoid lengthy toll charges.
International calling
A callback, in this sense is a method of making low-cost international calls via a third country, usually the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, where call charges are considerably lower.
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
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
as a Direct Dial-In (DDI) number. Where Caller ID
Caller ID
Caller ID , also called calling line identification or calling number identification or Calling Line Identification Presentation , is a telephone service, available in analog and digital phone systems and most Voice over Internet Protocol applications, that transmits a caller's number to...
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 America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n format, as most callback services are US-based, and callers are effectively calling from the US. For example, a number in Manhattan
Manhattan
Manhattan is the oldest and the most densely populated of the five boroughs of New York City. Located primarily on the island of Manhattan at the mouth of the Hudson River, the boundaries of the borough are identical to those of New York County, an original county of the state of New York...
would be dialled with the trunk code, area code and subscriber's number, as follows:
1 212 xxx xxxx
A call to London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
in the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, would require the international access code and country calling code, as follows:
011 44 20 xxxx xxxx
In the North American Numbering Plan
North American Numbering Plan
The North American Numbering Plan is an integrated telephone numbering plan administered by Neustar which encompasses 24 countries and territories, including the United States and its territories, Canada, Bermuda, and 16 nations of the Caribbean...
, 011 is used as the international access code, but in most countries, 00 is used, in line with International Telecommunication Union
International Telecommunication Union
The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...
'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
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
is calling a phone number in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, 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 callbackWeb Callback
Web Callback is a technology where a person can enter his or her telephone number in a form on a web site. The company who owns that web site will then receive the Web Callback request and a call center agent will call the person who made the request back on the number they entered.In some...
or mobile phone applications by companies such as GlobalTel
GlobalTel
GlobalTel is a phone service provided by InterActive Media Technologies, Inc. It provides Universal International Free Number , Direct dial, Callback and Calling card service to customers in over 200 countries. Additional services include CallMeBack, prepaid phone cards, carrier and switching...
, Alliance Communication, Save a Minute, Call2.com
Call2.com
Call2 is an international callback provider, founded in 1997 in the United Kingdom by Peter Farrer and merged by Andrew Try in 1999 to form Comxo Trading Ltd. Their offices are located just outside of London, England....
, Jajah
Jajah
Jajah is a VoIP provider, founded by Austrians Roman Scharf and Daniel Mattes in 2005. The Jajah headquarters are located in Mountain View, CA, USA, and Luxembourg. Jajah maintains a development centre in Israel...
or on Roaming SIM
Roaming SIM
Roaming SIMs can be defined as mobile phone SIM cards that operate on more than one network within their home country. They currently have two main applications, least cost call routing for roaming mobile calls and machine to machine....
s.
Legal status of callback
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, IsraelIsrael
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
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
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
or SMS
Short message service
Short Message Service is a text messaging service component of phone, web, or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices...
.
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
Broadband
The term broadband refers to a telecommunications signal or device of greater bandwidth, in some sense, than another standard or usual signal or device . Different criteria for "broad" have been applied in different contexts and at different times...
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 modemModem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
allows one computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
(the client) to establish a connection to another (the server) by dialing the server's telephone number
Telephone number
A telephone number or phone number is a sequence of digits used to call from one telephone line to another in a public switched telephone network. When telephone numbers were invented, they were short — as few as one, two or three digits — and were given orally to a switchboard operator...
. This is sometimes viewed as being insecure because there is no authentication
Authentication
Authentication is the act of confirming the truth of an attribute of a datum or entity...
of the call originator. One way to increase security
Computer security
Computer security is a branch of computer technology known as information security as applied to computers and networks. The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to...
is to enforce a modem callback protocol, which usually proceeds as a series of steps:
- The client computer calls the server computer.
- After a greeting the client identifies itself, usually with a user name.
- The server then disconnects the call.
- 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.
- 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
Billback
Billback or bill back is an accounting service and/or suite of software that is used for cost recovery.With a billback system, the client or payee is charged a percentage of the total cost of equipment, services, and venues of which they have already used...
purposes, allowing the originator to avoid lengthy toll charges.
See also
- Web CallbackWeb CallbackWeb Callback is a technology where a person can enter his or her telephone number in a form on a web site. The company who owns that web site will then receive the Web Callback request and a call center agent will call the person who made the request back on the number they entered.In some...
- GlobalTelGlobalTelGlobalTel is a phone service provided by InterActive Media Technologies, Inc. It provides Universal International Free Number , Direct dial, Callback and Calling card service to customers in over 200 countries. Additional services include CallMeBack, prepaid phone cards, carrier and switching...
- United World TelecomUnited World TelecomUnited World Telecom is a switch-based telecommunications service provider, located in Florida, USA, serving retail, wholesale, and corporate customers worldwide...