Interactive voice response
In telephony, interactive voice response, or IVR, is a phone technology that allows a computer to detect voice and touch tones using a normal phone call.  The IVR system can respond with pre-recorded or dynamically generated audio to further direct callers on how to proceed.  IVR systems can be used to control almost any function where the interface can be broken down into a series of simple menu choices.  Once constructed IVR systems generally scale well to handle large call volumes.

# Example usage
A caller dials a telephone number that is answered by an IVR system.  The IVR system executes an application which is tied to the number dialed DNIS (Dialed number information service). As part of the application, prerecorded audio files or dynamically generated Text to Speech (TTS) audio explain the options available to the caller. The caller is given the choice to select options using DTMF tones or spoken words. Speech recognition is normally used to carry out more complex transactions and simplifies the application menu structure.

# Typical uses
IVR systems are typically used to service high call volumes, reduce cost and improve the customer experience. Examples of typical IVR applications are: telephone banking, televoting, and credit card transactions. Large companies use IVR services to extend the business hours of operation. The use of the VUI (Voice User Interface) is designed to match the customer experience of the web interface. Companies have realised that access to voice services is impulsive and readily available. This is due to the high penetration of mobile phones.
Call centers use IVR systems to identify and segment callers. The ability to identify customers allows the ability to tailor services according to the customer profile. It also allows the option of choosing automated services. Information can be fed to the caller allowing choices such as: wait in the queue, choose an automated service, or request a callback. (At a suitable time and telephone number) The use of CTI(Computer Telephone Integration) will allow the IVR system to look up the CLI (Calling Line ID) on a network database and identify the caller. This is currently accurate for about 80% of inbound calls, but will increase as mobile phones become more popular. In the cases where CLI is withheld or unavailable, the caller can be asked to identify themselves by other methods such as a PIN or password. The use of DNIS (Dialled number information services) will ensure that the correct application and language is executed by the IVR system.
Voice Activated Diallers.
(VAD) Voice activated IVR systems are now used to replace the switchboard or PABX (Private Automatic Branch eXchange) operators. These are used in many hospitals and large businesses to reduce the caller waiting time. An additional function is the ability to allow external callers to page hospital staff and transfer the inbound call to the paged person.
Entertainment and information.
The largest installed IVR platforms are used for applications such as voting in TV game shows such as American Idol, X Factor, Big Brother, etc., which can generate enormous call spikes.  IVRs have also been widely used to take orders for mobile content, such as ringtones and logos, weather forecasts, crossword answers, and the whole spectrum of adult entertainment.
Anonymous Access.
IVR systems also allow callers to obtain data relatively anonymously.  Hospitals and Clinics have used IVR systems to allow callers to receive anonymous access to test results.   This is information that could easily be handled by a person but the IVR system is used to preserve privacy and avoid potential embarrassment of sensitive information or test results.
Clinical Trials.
IVR systems are used by large pharmaceutical companies to conduct global clinical trials and manage the large volumes of data generated.  The application used by the IVR in clinical trials is generally referred to as a Voiceform application. The caller will respond to questions in their preferred language and their responses will be logged into a database and possibly recorded at the same time to confirm authenticity.  Applications include patient randomization and drug supply management.

# Technologies used
DTMF signals (entered from the telephone keypad) and natural language speech recognition interpret the caller's response to voice prompts.
Other technologies include the ability to speak complex and dynamic information such as an e-mail, news report or weather information using Text-To-Speech (TTS). TTS is computer generated synthesized speech that is no longer the robotic voice generally associated with computers.  Real voices  create the speech in tiny fragments that are spliced together (concatenated) before being played to the caller.
An IVR can be utilized in several different ways:
- Equipment installed on the customer premise
- Equipment installed in the PSTN (Public Switched Telephone Network)
- Application service provider (ASP).
Many business applications employ this technology including telephone banking, order placement, caller identification and routing, balance inquiry, and airline ticket booking.
A simple  Voicemail system is different from an IVR in that it is person to person whereas an IVR is person to computer. IVR Voiceforms can be used to provide a more complex voicemail experience to the caller.  For example, the IVR could ask if the caller wishes to hear, edit, forward or remove a message that was just recorded.
An  Automatic Call Distributor (ACD) is often the first point of contact when calling many larger businesses.  An ACD uses digital storage devices to play greetings or announcements, but typically routes a caller without prompting for input. An IVR can play announcements and request an input from the caller. This information can be used to route the call to a particular skillset. (A skillset is a function applied to a group of callcentre agents with a particular skill)
Interactive voice response can be used to front-end a call center operation by identifying the needs of the caller.  Information can be obtained from the caller such as account numbers.  Answers to simple questions such as account balances or pre-recorded information can be provided without operator intervention.  Account numbers from the IVR are often compared to caller ID data for security reasons and additional IVR responses are required if the caller ID data does not match the account record.
IVR call flows are created in a variety of ways.  A traditional IVR depended upon proprietary programming or scripting languages, whereas modern IVR applications are structured similar to WWW pages, using VoiceXML, SALT or T-XML languages. The ability to use XML developed applications allows a Web server to act as an application server, freeing the developer to focus on the call flow.  It was widely believed that developers would no longer require specialized programming skills, however this has been proven to be misguided as IVR applications need to understand the human reaction to the application dialogue. This is the difference between a good user experience and IVR hell.
Higher level IVR development tools are available in recent years to further simplify the application development process. A call flow diagram can be draw with a GUI tool and the application code (VoiceXML or SALT) can be automatically generated. In addition, these tools normally provide extension mechanisms for software integration, such as HTTP interface to web site and Java interface for connecting to a database.
In telecommunications, an audio response unit (ARU) is a device that provides synthesized voice responses to touch-tone keypresses (DTMF) by processing calls based on (a) the call-originator input, (b) information received from a database, and (c) information in the incoming call, such as the time of day.
ARUs  increase the number of information calls handled and to provide consistent quality in information retrieval.

# Criticism
IVR is often criticized as being unhelpful and difficult to use due to poor design and lack of appreciation of the caller's needs .  Some callers object to providing voice response to an automated system and prefer speaking with a human respondent.  A properly designed IVR should provide the caller's needs promptly and with a minimum of complexity.