Interactive voice response equipment makes possible a variety of interactive services, in which users may control the operation of the service through the use of a DTMF telephone. These include transaction services, voice messaging, information retrieval and various supplementary services. This Recommendation is intended to provide general guidelines for the design of such services to ensure that they will be easy to use for customers and to provide some degree of consistency across services. It is intended to cover all such services in which the control by the customer is exercised through the 12 keys of a DTMF telephone set (the digits 0-9 plus * and #), and which provide prompting messages and responses in the form of recorded or synthesized speech. It does not include similar services controlled by voice commands interpreted either by human operators or by automatic speech recognition equipment.