At a recent computer convention I heard about a computer salesman telling a customer how easy it is to interconnect various devices as long as they follow the well-established RS-232-C standard. The customer then asked whether he needed a 25-pin male or a 9-pin female cable, and whether the data leads should be reversed or straight. The salesman’s answer was that the store carried every “standard” cable and if they do not have one, they will make it. . . .

This and many other vivid examples presented in this book, written by an electrical engineer with 30 years experience, are directed to those who wish to make their own decisions in the fascinating and increasingly costly domain of modern modems. The deregulation of the United States telephone industry resulted in a booming modem market because of rapid technological advances and competition.

The book effectively demonstrates that modem technology combines various disciplines of electrical engineering and computer science, such as circuit design, LSI, microprocessors, data transmission, and programming. The book is divided into four parts, covering

• (1) The principles of data communication and modulation/demodulation

• (2) Modems for the personal computer user

• (3) Modems for the commercial market

• (4) Diagnostics and testing

The second part shows the role of modems with personal computers, whose owners are becoming the principal users and purchasers of this technology. The reader will find a description of standard features and options available to the modem user and advice about their relative importance; emphasis is put on the Hayes standard and its various extensions. A description of the communication software and error detecting and correcting protocols is provided, followed by a look into the guts of modem chips.

The third part covers the features of modems that fulfill specific needs of corporations and universities by providing links between micros, minis, and mainframes. These modems require special transmission media rather than the public switched telephone network. A section on less common modem applications describes wide-band modems, multiplexers, modems with acoustic couplers, and security modems.

The fourth part discusses the important issue of what to do if the data get lost or garbled during the transmission. Various modem testing facilities, both built-in and stand-alone, are presented in their structural and algorithmic forms. The testing of transmission media is given particular attention as it requires a quantitative analysis of a telephone line (or a leased or privately owned circuit) to measure its parameters, including attenuation and delay distortions, noise, and phase jitter.

The body of the book ends with prospects for future modem generations. The appendices are very useful. They present a glossary of data communication terms, a directory of manufacturers, and a list of CCITT V recommendations and standards organizations.

The main advantage of this well-composed book, apart from its being the first reference guide for modem users known to me, are its obvious self-containedness, the breadth of its potential audience, which includes both professionals and amateurs, a friendly style of presentation, and its advisory character. This makes the process of reading it resemble consulting an expert system that the user may refer to either randomly or systematically.

Those who may remain a bit dissatisfied are designers who are looking for a tutorial on modem construction. Another possible complaint, though a relatively minor one, is the lack of information about any automatic recovery facilities in modem-based systems, as testing is only part of the whole, reliable communication life cycle. These weak points will not, however, hinder the book’s journey to the shelves and desks of a wide audience.