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With a voice portal system, also IVR system (Interactive Voice Response), callers can conduct partially or fully automated natural language dialogues via telephone or other acoustic media.

In practice, IVR also includes other telephony input options, such as multi-frequency dialling ("For sales, please press '1' now, for service, please press '2',..."). In telecommunications, IVR systems enable customers to interact with a company's host system via the keypad of a telephone or by voice recognition, so that information can be obtained using the IVR system. IVR systems can respond with pre-recorded or dynamically generated language to instruct users on how to proceed. IVR systems provided in a network are dimensioned for handling large call volumes.

Basic construction

IVR systems consist of the following components :

  • Automated Speech Recognition (ASR) with grammars / semantics for the interpretation of speech input (Natural Language Understanding NLU),
  • Speech synthesis (text-to-speech, TTS) for converting texts into computer-generated voices for speech output,
  • Dialog flow interpreter (e.g. VoiceXML browser) as frontend,
  • Business logic and databases for integration into business processes as backend.
  • Interfaces to IP network, telephone network,  DECT systems or audio connections,

Architektur von IVR-Systemen, Daniel Wimpff, 2008
Figure 1: Architecture of IVR systems

Biometric methods for speaker authentication ("The Voice as Password") are available and certified as secure by the German Federal Office for Information Security (BSI).

Due to the further development of speech recognition in recent years, dialogues consisting of entire sentences are possible. Natural Language Understanding (NLU) requires intelligence from the dialog partner. In order to use NLU effectively, the artificial intelligence of the dialogue system must keep pace with the possibilities of the speech recognizer. Now that the core technology has largely matured, new disciplines are coming into the focus of developers of speech dialog systems, e.g. dialog design.


IVR systems are used to process high call volumes, reduce costs and improve the customer experience. IVR systems can be used for mobile shopping, bank payments and services, orders from retailers, utilities, travel information and the weather report. IVR systems allow callers to retrieve data relatively anonymously. This is due to increased CPU performance and the migration of voice applications from proprietary code to the VoiceXML standard.