Interactive voice response (IVR) systems became a common means of delivering customer service in the late 1980s. These systems were designed to reduce or eliminate the need for human-in-the-loop customer support by automating many of the functions that human customer service representatives typically provide over the telephone with respect to processing of customer transactions. Thus, users (that is, callers) can now engage in such activities as checking train schedules, ordering a book or reporting problems with their television cable service by interacting with an IVR system. In addition, IVRs often automate call-routing functions so that the caller can be connected with the right assistance to handle their specific request. DIN EN ISO 9241-154 is to a large extent concerned with the design of the human-IVR system dialogue and related topics. Users typically interact with the IVR system through one of two methods: speech or touchtone (DTMF) input via the telephone keypad. If an IVR system is speech-enabled, it employs an ASR engine that recognizes the speech input from the caller. If it is not speech-enabled, it typically recognizes only touchtone input from the telephone keypad or, sometimes, TTY input. Speech-enabled IVR systems are a relatively recent development and many systems are now designed to accept both touchtone and speech within a given dialogue with a caller. The IVR system responds via hardware and/or software that presents synthesized, digitized or recorded speech to the caller and that may also present non-speech audio. The fact that there is no assumed visual display of information to the caller in these applications poses a challenge to dialogue designers because of the burden placed on the caller to navigate the application and process and remember the relevant information without the aid of any visual display. DIN EN ISO 9241-154 contains provisions specific to interactive voice response (IVR) systems, which may involve a combination of voice technologies, but are distinguished by the use of the telephone as the information transfer mechanism. These provisions assume no visual displays of information to the user beyond the labels on the telephone's keypad, with the notable exception of text telephones (TTYs), which have a visual feedback display. Although it is extremely important that IVR user interface designers take into account the cultural and linguistic aspects of the user interface that impact the intended user population, these aspects are beyond the scope of DIN EN ISO 9241-154. Similarly, because automatic speech recognition (ASR) performs differently for different languages and the technology continues to improve, it is beyond the scope of this document to provide detailed provisions on ASR user interface design generally. Rather, DIN EN ISO 9241-154 focuses on the design of IVR dialogues and discusses only those ASR user interface design issues that impact dialogue design. Many current IVR systems pose significant accessibility challenges to callers with disabilities. Some of the provisions in DIN EN ISO 9241-154 were developed specifically to accommodate callers with special needs, particularly those who are deaf or who have hearing impairments. DIN EN ISO 9241-154 provides provisions for the design of IVR dialogues in speech-enabled and touchtone-based IVR systems. Therefore, the focus of this standard is on the interface between the caller and IVR software and application databases, which is mediated by the hardware and software that recognize speech and/or touchtones, and which present speech output to the caller. Both ASR systems and DTMF recognizers place constraints on the design of IVR dialogues and those constraints have been considered in developing the provisions of DIN EN ISO 9241-154. However, DIN EN ISO 9241-154 is not intended to address the design of ASR or DTMF user interfaces generally, for two reasons. First, the technology, particularly for ASR systems, is still evolving, and second, many ASR user interfaces are designed to include a visual display (for example, ASR dictation applications), which IVR applications are not assumed to have. Lastly, most of the provisions for speech-enabled dialogues are intended for use with grammar-based IVRs. Although some of the same principles apply to natural language systems (that is, applications that use statistical language models), detailed design provisions are not included for these applications in this standard because natural language understanding is implemented via a distinct technology and the use of natural language in speech-enabled IVRs is still evolving. There are also some aspects of applications design that are different for natural language dialogues, relative to grammar-based ones, in addition to the differences in dialogue design that relate to speech recognizers specifically. Unless specified otherwise the provisions in this document are intended to be compatible with ISO/IEC 13714 "Information technology - Document processing and related communication - User Interface to telephone-based services - Voice messaging applications". The committee responsible for this standard is NA 023-00-04-05 GAK "Gemeinschaftsarbeitskreis NAErg/NIA: Benutzungsschnittstellen") ("Joint working group NAErg/NIA: User interfaces") at DIN.