Integrated Services Digital Network

CHAPTER 2The network before ISDN

DOI: 10.1201/9781003420408-2

2.1 Introduction

To understand the need for the ISDN and the requirements for its implementation we must first understand the established services and the nature and requirements of the existing networks that are to be converted to the ISDN. This preparatory treatment must necessarily be brief and must assume that the reader has considerable prior understanding of telecommunications. As background reading, references 2, 9 and 10 are suggested.

The proposal to introduce the ISDN is predicated upon the existence of a digital network and the possibility of providing the digital interface at the user’s premises. The worldwide public telephone network, however, is presently predominantly ...