15.1 Introduction

This chapter considers the design and deployment of an application solution that spans both existing TDM networks and emerging VoIP networks. The first Recorded Information Distribution Equipment (RIDE) system was deployed by BT in the late 1980s [1] to provide economic mass access to recorded announcements. The system was designed for excellent availability for applications with a high customer profile, generating a very large number of calls. Services deployed on RIDE include announcements for national code changes, timeline (the 'speaking clock') and televoting.

By the end of the 1990s it was recognised that the system needed to be replaced as key hardware components were becoming obsolete, the system could not support the more sophisticated voice processing capabilities required, and there was a need to deliver similar services (e.g. a 'televote') into Internet-hosted applications. These requirements are typical of many TDM-based network solutions currently deployed. The chosen replacement system, supplied by Telspec plc, is based on a 'distributed service node' architecture that has elements of the original RIDE architecture, together with features drawn from intelligent network and computer telephony integration (CTI) architectures [2].

The use of VoIP is particularly suitable for distributing live audio of the kind used in the RIDE solution. This is because these unidirectional audio feeds are not conversational. The usual problem of transmission delay in a VoIP network (see Chapters 2 and 3) is therefore not generally an issue. As the amount of VoIP traffic is also fixed,...