Introduction to Modem Technology
Modems are offered in several forms for use in various applications. Stand-alone modems, for instance, are self-contained, with internal power supplies, and are used with separate information products. Where a number of circuits come togetheras at the interface to a large computer systemrack-mounted modems are often used, sharing power supplies and packaging. Modems can also be packaged inside an information product (such as a personal computer). Such integrated modems usually lower overall cost but increase the complexity of the information product and the cost of designing it. Integrated modems are usually offered as an option, because to standardize on a particular modem type with a product might restrict the usefulness of the product. This article provides a brief introduction to three popular types of modems: voice-grade, cable, and ADSL.