Switching principles
S. F. Smith · Institution of Engineering and Technology eBooks · 1997
Preceding Chapters have described the nature of telecommunication networks and identified the need for switching at the nodes of a network. The users of communication terminals, such as telephones and data terminals, make calls to other users over a common network. Such networks may be public or private, but all have the characteristic that communication paths are provided to users only when they require them, usually on demand but sometimes after a delay. To provide permanent paths for all possible communicating groups of users would be impractical and uneconomic, so the networks contain exchanges (central offices) at their nodes to set up and break down paths as required. This Chapter is concerned with the general principles applying to the design of exchanges and some of the practical implementations of them. Later Chapters will deal with these topics in greater depth.