Chapter 5. Interactive Voice Response (IVR)

An interactive voice response system lets computer systems interact with telephone callers, who provide input to the system either by pressing the keypad on their telephone set (DTMF, "dual-tone multi-frequency" keying, aka Touch-Tone®) or by saying something (natural language speech recognition). Most IVR systems provide selection menus for routing calls without requiring operator intervention, but modern IVR systems can also be very complex applications that handle information or control equipment.
The basic principle common to all IVR systems, however, is that the caller is read a menu and chooses options from that menu to perform actions, or, alternatively, enters information (in numerical format, through pressing the keypad). IVRs can be used to obtain stock quotations, train schedules, and weather reports; they can also be used for automated purchasing systems, such as for concert tickets. The potential applications are limited only by your imagination.
Systems vary in their complexity. The most advanced generate spoken text "on-the-fly" using text-to-speech (TTS) systems and accept spoken user input with speech recognition. When properly implemented they can provide a high level of user-friendliness, but implementation is so complex that they are rarely used, except in larger organizations.[22]
The simplest form of IVR is also the most common. Pre-recorded messages are played to the caller; the caller responds with DTMF keypad input, which Asterisk can recognize easily in the default install.
Public opinion on IVRs is divided. Some people find them a helpful form of automation, while others find them exceedingly frustrating. This is usually the result of poor menu design or speech recognition with a high failure rate. A well-functioning IVR can be pleasant for the customer, but a poorly implemented one can scare her away.[23]Take care when planning an IVR system. Pay special attention to menu design and allow adequate time for a clean development and deployment. Aggressive testing and post-deployment monitoring of premature hang-ups should be part of your routine. Remember that IVR systems are not an end in themselves, nor are they a panacea. Think of your customer!

[22] LumenVox makes a speech recognition kit for Asterisk. See

[23] The increasingly multi-ethnic nature of society everywhere means that speech recognition should be implemented with caution, as accents can be problematic.