Modems and Multiplexers

Abstract

Modems and multiplexers are essential components of data communications networks. Both are needed to support communications between a central site processor and remote terminals or network nodes. Modems are necessary to support digital communications over long distances. They convert digital signals from data terminal equipment to an analog form for transmission over analog communications facilities, and reconvert the analog signal to a digital form at the other end. Multiplexers combine transmissions from several sources on one line, eliminating the cost of several lines and modems between two points to support independent transmissions. Modems and multiplexers are available from a multitude of vendors. The products offered by these vendors differ in application, performance, and price. Selecting the appropriate modems and multiplexers to satisfy user requirements is often a compromising task requiring considerable time and effort. Network managers and planners need a sound understanding of data communications technology and an awareness of the available products and their specifications to design a cost-effective network using modems and multiplexers that meet current and future needs. This chapter provides a basic understanding of modem and multiplexer technology, explains essential operating parameters, and describes general application areas.